O'Reilly Surname Meaning, History & Origin

O’Reilly Surname Meaning

O’Reilly is derived from the Gaelic O’Raghailligh, meaning descendant of Raghaillach (from ragh, a “race,” and ceallach meaning “gregarious”).

The story goes that Raghaillach was killed at the Battle of Contarf in 1014 while fighting alongside Brian Boru.  His descendants, the O’Reilly sept, followed Celtic traditions with their chief being inaugurated at an ancient stone circle on Seantomon hill outside of Cavan town.

Today it is O’Reilly more in Ireland, Reilly more outside. And Reilly has often become Riley.

O’Reilly Surname Resources on The Internet

O’Reilly, Reilly and Riley Surname Ancestry

  • from Ireland (Cavan)
  • to Spain, England, America, Canada and Australia

Ireland.  The O’Reillys were the most powerful sept of the old Gaelic kingdom of Breffny which comprised present-day Cavan and surrounding counties. For a time they lay under the shadow of the stronger O’Rourke clan. They also fell foul of Norman incursions into their territory.

However, a new chief, Giaolla Iosa O’Reilly, re-established O’Reilly control in the early 1300’s and helped develop Cavan as a thriving market town. The O’Reillys were able to maintain their position for over two hundred years. Their strongholds were Clogh Oughter castle and Tullymongan hill outside of Cavan town.

The O’Reilly were widely involved in trade at this time. They created their own coinage by “clipping” English coins and at one time reilly was a term for Irish money. It has also been suggested that they lived well, as the phrase “the life of Reilly” suggests.

The English were eying Breffny in Tudor times. They captured Cavan town in 1600. Edmund O’Reilly of Kilnacrott was killed at that time, the last of the O’Reilly chiefs of Breffny, and lost his estates.

In the 1640’s, during the Irish rebellion, the O’Reillys – led by Edmund’s son Myles the Slasher – retook Clogh Oughter castle and were temporarily in power again. But Clogh Oughter fell to Cromwell in 1653 and the English process of dispossession and confiscation of lands continued.  Hugh Reilly of Cavan supported the luckless Stuarts in 1690 and followed James II into exile.

The O’Reilllys suffered for their Catholic faith during the penal times. Some “wild geese” became mercenaries abroad. Many O’Reillys emigrated later. In Ireland the largest numbers are in Dublin. O’Reillys are still numerous in what was Breffny – Cavan and neighboring Longford.  The name is also quite common in Fermanagh and Monaghan. Some 60% are called O’Reilly and 40% Reilly.

Spain and Austria. Alejandro O’Reilly left his home in Baltrasna, Meath during the penal times to fight for the Spanish army in the Irish Brigade. A Field Marshal and Count, he was sent to Cuba in 1769 to quell disturbances there. One of Havana’s streets is called Calle Orely and his descendants are still to be found there.

Colonel Edmund O’Reilly commanded O’Reilly officers in the Spanish and Austrian armies during the 1700’s. Count Andrew O’Reilly of Westmeath was a Field Marshal in the Austrian army who, as Governor of Vienna, had the humiliation of surrendering the city to Napoleon in 1809.

England. O’Reillys and Reillys came to England in the 19th century and primarily to Lancashire. James Reilly was in Manchester sometime by the 1820’s. He and his sons were cabinet-makers and skilled ones too. Their trade expanded until by the late 1800’s they had even begun to export their furniture.

But many Reillys arrived and lived in poverty and overcrowding. Eight members of a Reilly family together with eleven lodgers were recorded as living in a tiny cellar dwelling on John Street in Manchester during the 1850’s.

America. O’Reilly emigration to America also stepped in in the 19th century. Many left during the famine times. John Riley came in the 1840’s, started off fighting for the US Army in the Mexican War, and then left them to fight on the Mexican side.  Father Thomas O’Reilly arrived from Cavan in 1857.  He was the man who saved the city of Atlanta from complete destruction during the Civil War.

Andrew O’Reilly came to America via Canada. As also did James O’Reilly:

“Articles about James O’Reilly who emigrated between 1849 and 1852 suggest that it took him eight weeks to come by a boat that was shipwrecked and landed in Newfoundland.  He came to Troy, New York where he worked as a farm laborer for three years. Perhaps he, like many other Irish emigrants, sent money home to his family, enabling his brother Michael to follow him to America and perhaps helping to keep those who stayed at home alive.”

John Boyle O’Reilly was a man who made the journey to America through unusual routes. He had been transported to Australia in 1867 because of his involvement in militant Fenian groups. But he escaped two years later, made his way to Boston, and became a supporter of Irish causes there and the well-respected editor of the Pilot newspaper.

Alexander O’Reilly, a descendant of the O’Reillys in Cuba, grew up in Philadelphia and became a well-known doctor. He was personal physician to President Cleveland and surgeon general to the US Army in the early 1900’s.

Canada. Peter O’Reilly, the son of an Irish father and English mother, left Ireland in 1859 for the opportunities that might be presented in the new western colony of British Columbia. He prospered there in forty years of Government service. In 1868 he bought a large home in Victoria which was lived in by his descendants until 1975. It is now known as Point Ellice House and is preserved as a museum.

Australia. O’Reillys and Reillys who came to Australia included:

  • Joseph Reilly, who having retired from the British army came to Western Australia from Meath in 1853 with his wife Mary and settled in Perth.
  • Peter O’Reilly who arrived in New South Wales from Ulster in 1865. His grandson Bill, nicknamed “Tiger,” was the great spin bowler of the Australian cricket team in the 1930’s.
  • and Thomas O’Reilly and his family who left their native Roscommon for Melbourne on the Lady Jocelyn in 1875. They settled in Numurkah.

The Green Mountains on Australia’s Gold Coast was first settled in 1911 by an O’Reilly family. They took up a number of small dairy farms before consolidating their holdings around what is now an internationally famous guesthouse in the rainforest.

O’Reilly Surname Miscellany

The O’Reillys at Cavan.  By the late 1300’s the O’Reillys had secured their land and moved their seat from Clogh Oughter Castle to Tullymongan Hill.  The castle they built there attracted settlers and a new town grew up in the hollow beneath Tullymongan Hill and the surrounding hills.  No one gave the town a name. It was simply known as an Cabhan, Gaelic for “the hollow.”  To English ears the “’bh” sounded like “v” and so the name Cavan emerged.

The O’Reilly Chief or Breifne was known simply as “The O’Reilly” in line with Celtic tradition.  The ancestral inauguration site of the Chief was at an ancient stone circle on Seántomon Hill three miles northeast of Cavan town.  The stones were fondly known as the fingers of Fionn McCool, a legendary Celtic hero.

Myles the Slasher and His Progeny.  Myles O’Reilly, better known as Myles the Slasher, led the Irish resistance to the English during the 1641 rebellion.  For a time the whole of Cavan fell to his insurgents and Myles defeated a Scottish army under General Munro at the battle of Benburb. But the Scottish fought back and Myles died in 1644, bravely standing up against their cavalry on the bridge at Finea.

His son Colonel John Reilly lived at Baltrasna in county Meath and was said to have been the first member of the sept to drop the “O” prefix from the name. He raised a regiment of dragoons for King James and served in the Jacobite army in the Williamite war.  He was allowed to keep his lands after the war was lost and he died at Batrasna in 1717.

John left a son, Thomas, who was the father of Alexander or, as he became, Alejandro O’Reilly in Spanish service.

Count Alejandro O’Reilly.  Alejandro O’Reilly from Baltrasna in county Meath had fought for Spain with the Irish Brigade.  He rose in Spanish ranks to become a Field Marshal, Governor of Madrid, Captain General of Andalusia and Governor of Cadiz.

In 1769, he was dispatched to New Orleans with a strong military force to put down a popular uprising.  His affability allayed all suspicion and, after checking out the leaders, he invited them to a reception where he had them all arrested.  Five were put to death and the others were imprisoned in Havana.  That put an end to the rebellion.

Count O’Reilly’s rule in Spanish America was regarded as liberal and enlightened.  His descendants have been in Cuba for two centuries where, as the Counts of Castillo and Marquis of San Felipe y Santiago, their lineages can be found in the archives of  Havana.

Reilly and O’Reilly.  Today it is O’Reilly more in Ireland, Reilly more outside.  The table below shows the approximate numbers:

Numbers (000’s)   O’Reilly   Reilly
Ireland   19   14
UK   10   19
America    4   17
Elsewhere   12    7

John Riley and the San Patricios.  The San Patricios were a group of Irish-Americans who, during the Mexican War of the 1840’s, deserted the US Army to fight for the Mexican leader Santa Anna.  Their reasoning was twofold – they felt that they suffered discrimination by non-Catholic members of the American army and they also disapproved of the treatment of Mexican civilians, priests and nuns during the war.

John Riley led the San Patricios in five major battles against the Americans, ultimately establishing his unit as a force to be reckoned with.  To this day, the flag of the San Patricios continues to fly in his hometown of Clifden in county Galway and a sculpture stands there in honor of John Riley and the men who served under him.

Reader Feedback – Father O’Reilly in Atlanta during the Civil War.  There was another less well-known O’Reilly. Father Thomas O’Reilly prevented the complete destruction of the city of Atlanta, Georgia during the American Civil War.

O’Reilly had been appointed pastor of the Church of the Immaculate Conception and his time during the Civil War had been consumed with pastoral care of both the Confederate and Union soldiers, many of whom were Irish. By 1864 Atlanta had fallen to the advancing Union army and all citizens were advised to leave as Sherman planned to burn the city down.

O’Reilly made clear that his church was not to be burned.  In fact none of the churches were to be burned, including other municipal buildings. Sherman sent General Henry Slocum to intimidate O’Reilly.  But even under the threat of assassination, all threats fell on deaf ears.

In short, O’Reilly said that nobody liked a priest killer or a church burner, that it was a sin against God and threatened Slocum by saying that he had left instructions that in the event of any harm coming to him or the churches of Atlanta, all Irish soldiers were to drop arms, and all Catholics in general would be excommunicated if they were a party to it.

Slocum was impressed with this tenacious little Cavan man who had left his home in Ireland in 1857 for America. Therefore an agreement was made that five churches in Atlanta, including ones which were not Catholic, were to be saved – along with a number of municipal buildings. Cleverly, O’Reilly suggested that the knock-on effect of burning the houses near these buildings heightened the risk of the spread of fire and therefore were not to be torched either.  Thus he saved over four hundred homes and buildings.

He strove to rebuild Atlanta but unfortunately he didn’t live long enough to see the fruits of his labor. By 1872 O’Reilly had died at the age of 41. Seemingly he had contracted yellow fever on the journey from Ireland to America a number of years earlier which weakened him considerably.

Although there is a statue in commemoration of O’Reilly’s efforts in Atlanta today, his loss was obviously felt the hardest amongst his family back home in Cavan. Interestingly he took out life insurance for ten thousand dollars – leaving one thousand to his parish in Atlanta, one thousand to his parish in Cavan, five hundred dollars to each of his siblings (of which there were many), and five thousand dollars to Bridget O’Reilly, his mother and my great great great grandmother. The story of his life, although not widely known, reigns supreme in our family history.

Olwen Carolan (Olwencarolan@gmail.com).

Andrew and Michael O’Reilly.  Andrew and Bridget O’Reilly from Cork fled Ireland during the potato famine in the early 1850’s and made it with their three children to Canada. The 1861 Canadian Census has them living in Halliwell township, Ontario.  Their son James moved across the border to Faribault, Minnesota and that was where Andrew and Bridget were buried in 1888 and 1889.

It was thought that Andrew had a brother named Michael. But nothing more was known about him. However, Chip Hutchinson, a great great grandson of Michael, managed to track down Andrew’s descendant Bill in 2008, thereby reuniting the two sides of the family.

Reader Feedback – Andrew and Michael O’Reilly.  Would like to have a contact address for Chip Hutchison, descendent of the Andrew and Michael O’Reilly family.  I suspect Chip’s great great grandfather and my great great grandfather may have been brothers or some other close relation.

Please share this email with Chip, along with my email address.  Thank you so much.

Dean O’Reilly in Oregon (oreillyco@gmail.com)

Reader Feedback – O’Reillys in Ontario, Canada.  Alexander, my second times great grandfather, was born in 1813 in Upper Canada (Ontario).  I am looking for his parents and siblings.

Alexander’s wife was Mary Ann (Marianne).  Their children – Elizabeth, Adelia, Miles, Huldah, Sarah and my great grandfather Eli Abrahams – were all listed in the 1851 Canada West census as living in the Dunnville, Canborough, and Moulton area of Ontario area.  Alexander’s occupation was listed as grocer.   The family oral history says that his father immigrated from Ireland as a stowaway on a ship as a teenager.

Will welcome information anyone might share to help us make a family connection.

Dean O’Reilly in Oregon (oreillyco@gmail.com)

O’Reilly and Reilly Names

  • Giaolla Iosa O’Reilly restored the O’Reilly position in Cavan in the early 1300’s and founded the Franciscan Abbey.
  • Myles O’Reilly, known as Myles the Slasher, became a folk hero in Ireland for his stand against the English during the Irish rebellion of the 1640’s. He died in battle in 1644.
  • John Boyle O’Reilly was an Irish Fenian leader who escaped British prison in Australia in 1869 to become a well-known journalist and writer in America.
  • Tony O’Reilly was an international rugby player for Ireland who became the CEO of Heinz Corporation.
  • Paddy Reilly is one of Ireland’s best-known balladeers.
  • Bill O’Reilly was a prominent face on American cable TV through his O’Reilly Factor show on Fox TV.

O’Reilly and Reilly Numbers Today

  • 29,000 in the UK (most numerous in Lancashire)
  • 34,000 in America (most numerous in New York)
  • 52,000 elsewhere (most numerous in Ireland)

O’Reilly and Like Surnames 

The Irish clan or sept names come through the mists of time until they were found in Irish records such as The Annals of the Four Masters.  The names were Gaelic and this Gaelic order was preserved until it was battered down by the English in the 1600’s.

Some made peace with the English.  “Wild geese” fled to fight abroad.  But most stayed and suffered, losing land and even the use of their language.  Irish names became anglicized, although sometimes in a mishmash of spellings.  Mass emigration happened after the potato famine of the 1840’s.

Some surnames – such as Kelly, Murphy and O’Connor – span all parts of Ireland.  But most will have a territorial focus in one of the four Irish provinces – Leinster, Munster, Ulster, and Connacht.

Leinster in SE Ireland covers the counties of Carlow, Dublin, Kilkenny, Offaly, Laois, Longford, Louth, Meath, West Meath, Wexford, and Wicklow.  Here are some of the Leinster surnames that you can check out.



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Written by Colin Shelley

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