O'Brien Surname Meaning, History & Origin

Select O’Brien Meaning
The early history of the O’Brien
clan is as a Dalcassian tribe in SW Ireland and then with
Brian Boru, the legendary king of
Ireland who defeated the Norsemen at Clondorf in 1014 but died in the
process. The Ui Braians ruled over
Munster after Brian Boru’s death and, as O’Briens, emerged as one of
dynastic families of Ireland.
Today, due to emigration, there are more O’Briens
outside Ireland than within, with the largest number being in America.There
are many name variants of O’Brien around the world, including Bryan,
McBryan, O’Brian, O’Bryan, Bryant, and Breen.

O’Brien Resources on

Select O’Brien Ancestry

The Rock of
Cashel in Tipperary was the traditional seat of the Kingdom of Munster,
which the
O’Briens would hold until the 12th century.
After that time the territory was divided and they ruled over
kingdom of Thurmond in present-day Clare instead.

Their ancestral home in Thurmond was
Dromoland castle. The O’Brien’s rule would last until 1542 when
O’Brien surrendered its sovereignty to the new English kingdom of
Ireland under
Henry VIII.

Over the subsequent
centuries there were to be many O’Brien branches. The Earls of
representing the main descent, did tend to side with the English. Other O’Briens, although they had accepted
English titles, often ended up opposing the English cause:

  • Murrough
    O’Brien, the Earl of Inchiquin, having supported the
    English in 1641, switched sides and left Ireland for France and French
    service in 1650,
    his grandson was later to return in 1703.
  • while
    the Viscounts Clare left in 1690 and never returned.
    They raised the famous Irish brigade known as Clare’s
    and were fighting for France until the last of them
    died in

O’Briens at
Comeragh castle
in Waterford were almost wiped out
by Cromwell in 1656. After taking the
castle, he hanged four of the O’Brien brothers.
The fifth, John, managed to escape and from him came the
O’Briens of

The history of
the O’Brien clan
, up to the end of the 18th century, was
first compiled by John O’Donoghue in the book he published in 1860.

In the 19th century, from an
O’Brien Clare line, came William Smith O’Brien, an Irish nationalist
and one of
the leaders of the Young Ireland rebellion of 1848.
This led to his arrest, trial, and
transportation to Australia. Other
O’Briens of varying backgrounds were also to become engaged in the
cause of
Irish nationalism at this time.

Today in
Ireland, O’Briens are mainly found outside Dublin in the Munster
counties of
Clare, Limerick, and Cork.

America. A number of O’Briens came to
in the second half of the 18th century, including Morris
O’Brien who came to Machias in Maine. His son Captain Jeremiah
O’Brien was one of the early
American heroes
of the Revolutionary War. In 1775 he
captured a British armed schooner off Machias in the first naval
engagement of
the war. His son Jeremiah ran a
manufacturing and shipping business in Machias and was active in local

Born in Ireland in 1827, Hugh
O’Brien moved with his parents to Boston when he was five.
He prospered there as a printer. In
1885, he took the office of mayor of
Boston, the first Irish-born and the first Catholic to do so in a city
previously run by native-born Protestants.
A much later Boston celebrity is the talk-show host Conan
O’Brien who
grew up in a middle-class family in Brookline.
His forebears had immigrated to Boston from county Kerry at the
time of
the potato famine.

Canada. The
O’Brien name in various forms was evident in
Newfoundland by the late 18th century.
John O’Brien came to St. John’s around 1818.
A dairy farmer, he built Thimble Cottage in
the outskirts of the town. It still
stands, with the third generation of O’Briens living there.

O’Briens were also part of
the Irish community in Antigonish county, Nova Scotia.
The 1838 census listed O’Briens in Dorchester
and Tracadie townships. Richard Baptist
O”Brien, later a fervent advocate of Irish home rule, spent time as a
priest in
Antigonish county in the 1840’s. Michael
J. O’Brien, the railway industrialist, was born at Lochaber in 1851. He and his son Ambrose were influential in
the founding of the Montreal Canadiens and the National Hockey League.


O’Brien Miscellany

O’Brien Early History.  The O’Brians emerged as chiefs of the Dalcassian tribe in SW Ireland which claimed a descent from the legendary Cormac Cas back
in the 3rd century.   This claim may have been fanciful.   The Dalcassians in fact first began to
appear in history in county Clare around the 8th century.
Their chief was crowned king of Thomond (or
north Munster) two centuries later.  His
son Mathgamain mac Cennetig was to expand their territory further,
according to
the Annals of Ulster, and he captured
the Rock of Cashel (in present day Tipperary), thereby becoming the
king of
Cashel and Munster.

His younger brother Brian Boru, born
around 940, first made himself king of Munster, then subjugated
Leinster, and,
eventually became the King of All Ireland, in the process ending the
domination of the Ui Neills.  He died in
1014 in the celebrated battle of Clondorf when the Norsemen were
defeated.  He was the founder of the
O’Brien clan that was to follow.

The History of the O’Brien Clan.  The first O’Brien history, The Historical Memoir of the O’Briens, was written by John
O’Donoghue and published in 1860.  It told
the story of the O’Briens from Cormac
Cas through Brian Boru and up until the end of the 18th century.

The author used as his source material the various
reference works of Irish history that were available to him at the
time, such
as The Annals of the Four Masters, The
Annals of Innisfallen
, The Annals of Ulster, plus
the works by
John O’Donovan and other scholars of Irish history.
From these sources came the development of
the O’Brien clan pedigrees.

which has only been available in limited numbers, has recently been
with a foreword by Morgan Llewelyn (who has written the story of Brian
and portraits of the notable O’Briens in history.

is an update on this O’Brien history
which has taken the story to 1946.

The O’Briens at Comeragh Castle.  The first
reference to the O’Briens of Comeragh castle, at the foot of the
mountains in Waterford, was in 1549 when Anthony O’Brien obtained a
pardon from
the English government.   However,
were never safe from the English.  The
castle was besieged unsuccessfully in 1619.
During Cromwell’s time Derby O’Brien, the head of the O’Brien
family at
that time, was taken in 1656 and he died in captivity.

Then, after fierce
resistance from the five sons of Derby O’Brien, Comeragh castle was
captured by
Cromwell.  He hanged four of these
sons.  The fifth son, John of
Kilnafrahane, managed to escape to the coast and he made a home for
himself near
Helvick Head.  From him came the O’Briens
of Ballyetragh who were there through the 18th and 19th centuries.

Clare’s Dragoons.  Clare’s Dragoons,
initially named O’Brien’s Regiment
after its originator Daniel O’Brien the 3rd Viscount Clare, had been raised
as a mounted dragoon regiment from Limerick to support the dethroned
James II against the army of William or Orange in Ireland.

the defeat at the Battle of the Boyne,
the regiment reformed in France, first in 1689 and later in 1696. It fought under the name of Clare’s Dragoons
in the service of France in various campaigns between 1696 and 1774.

marching song has survived.   The
stanza which follows shows the O’Brien

“Another Clare is here to lead,
The worthy son of such a breed

The French expect some famous deed,
When Clare leads on his bold dragoons.
Our colonel comes from Brian’s race,
His wounds are in his breast and face,
The bearna baoghil is still his place,
The foremost of his bold dragoon.

Viva la, the new brigade!
Viva la, the old one too!
Viva la, the rose shall fade
And the shamrock shine forever new!”

Early O’Briens in America.  Morris O’Brien had arrived in Machias, Maine from Cork in Ireland in 1765.  He was aged about fifty then and engaged himself in the lumber business, operating a
sawmill with
his sons.  He died in Machias in 1799 and
his tombstone read:

“Here lie deposited
the remains of Morris O’Brien, who died June 4, 1799, aged 84 years.

‘Come think on me, as you pass by,

As you are now, I once was too;
As I am now so you must be,
Prepare for death to follow me.’”

He was an
American patriot and the father of five sons, including Captain
O’Brien, who all distinguished themselves during the Revolutionary War.

other early O’Brien arrivals in America
can be seen in the table below.

Date O’Brien Vessel
1760’s Philip O’Bryan Russ Dublin to Maryland
1764 James and John Brien Hannah Cork to Boston
1766 Timothy Bryan Wilmott Cork to Boston
1767 Mary and Elizabeth O’Brien Ann
& Margaret
Ireland to Boston

O’Bryan is believed to have come from
Armagh.  He appeared on the census
Frederick county, Maryland in 1776 and served in the Maryland militia
the Revolutionary War.

The O’Briens and Thimble Cottage.  John O’Brien had come to Newfoundland from Ireland
around 1818 and started his farm in fourteen acres of land that he had
in Freshwater valley near St. John’s.   He
established a commercial dairy farm there and
sold his milk to housewives and shopkeepers in the west end of St.

He had built two farmhouses on his land
before he started work on a third one, on Nagle Hill in St. John’s, in
1850.  It was to be situated on a narrow,
steep, winding gravel road on Nagle Hill, nestled in a forested grove
overlooking much of the city of St. John’s.

for his son Timothy, it took two winters to gather sufficient
materials from the nearby forest to build the house.
He made the chimney from locally-gathered
stone and sheltered the structure with locally-made spruce shingles.  The two-and-a-half-storeyed salt-box house
has a sloping roof which makes the structure a single storey at the
rear where
the kitchen is located.

house is
typical of a 19th century Newfoundland Irish farmhouse.
It is the sole survivor of approximately
twenty similar homes that were once common in the Freshwater valley

Cottage survived the 1892 fires and
has been continuously lived in by the O’Brien family since the time it
built.  In 1992 the Heritage Foundation
of Newfoundland and Labrador rewarded the efforts of the O’Briens to
their land and home when Thimble Cottage was declared a Registered
Structure.  Aly
O’Brien who died there in 2008 was said to have been the last Gaelic
speaker of


Select O’Brien Names

  • Brian Boru, the legendary 10th century Irish king, left his name to the O’Brien clan.
  • Murrough O’Brien, known as
    Murcha of the Burnings, played a controversial role in mid 17th century Irish politics. He was made President of Munster for expelling the Catholics and then became a Catholic himself.
  • William Smith O’Brien was the 19th
    century Irish nationalist who led the 1848 Young Ireland uprising.
  • William O’Brien was the Irish nationalist who founded the United Irish League, the forerunner of Sinn Fein.
  • Edna O’Brien is an Irish novelist and short story writer who novels were first banned in Ireland.
  • Aidan O’Brien is a very successful Irish horserace trainer.
  • Conan O’Brien is an American
    comedian and late-night talk show host.

Select O’Brien Numbers Today

  • 37,000 in the UK (most numerous
    in Lancashire)
  • 60,000 in America (most numerous
    in New York)
  • 108,000 elsewhere (most numerous in Ireland)


Select O’Brien 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.

Munster in SW Ireland covers the counties of Clare, Cork, Kerry, Limerick, Tipperary, and Waterford.  Here are some of the Munster surnames that you can check out.



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