McMahon Surname Genealogy

is an anglicized form of the Old Gaelic MacMathghamhna, a patronymic from
the byname Mathghamhain,
meaning “bear.”  Two distinct septs of this name existed in
Ireland, one in county Clare and the other in and around present-day
The first specific recording of a McMahon in Ireland – dating from the
1170’s – was, however, the McMahon name adopted by Reginald FitzUrse
after he had fled to Ireland following the murder of Thomas a’Beckett.

McMahon Resources on

McMahon Ancestry

There were two distinct septs and territories for the McMahons in

The first belonged to Thomond, now county Clare.  They were descended from Mathghamha, son of Murtagh Mor O’Brien, king of Ireland, who died in 1119.  The lands of Corcabaskin, Moyarta, and Clonderlaw in west Clare were considered their territories.  Here the McMahon name is still numerous.  The remains of Carrigaholt castle dominate the harbor at Loop Head in county Clare.  Teige McMahon, the last of the lords of Corcabaskin, lived there.  He died in 1601 after the battle of Kinsale, accidentally killed by his own son.

The other McMahons became lords of Oriel in the 13th century (Oriel being an ancient kingdom encompassing Armagh, Monaghan, and parts of Down, Louth and Fermanagh).  The first of these McMahons was Niall McMahon ladrannaibh
or bandit.  Chiefs of the clan were crowned at Lough Leck in present-day Monaghan.

Their history over the next three hundred and fifty years appears to have been one of continuous fighting, not only with other septs but amongst themselves.  However, it was the English that caused their eventual demise.  After the Irish uprising of 1641 had been crushed the McMahons were no longer listed as landowners in Monaghan.  Their last chieftain, Hugh Oge McMahon, had in fact been a lieutenant colonel in the Spanish army.

McMahons struggled after the Gaelic order ended.  A few joined
“the wild geese” and others began to emigrate in the 19th
century.  In 1890 the McMahons were most plentiful in Ireland in
Clare, Monaghan (where they were the third ranked surname), Limerick,
and Dublin.

  John McMahon,
an Irish doctor from Limerick, had come to France to
escape the English penal laws in Ireland.  He married into the
aristocracy and became the Marquis de
MacMahon.  His son fought on the American side in the
Revolutionary War; and his grandson Patrice was a French general who
went on to be a Marshal of France and the first President of the
Third Republic in the 1870’s.

England and Scotland.
McMahons came to Lancashire and to Glasgow in the 19th century because
of the industry and the jobs there.  Philip McMahon, for instance,
came to Manchester in the 1830’s, marrying Ann Connor there.  One
family line in
Scotland  began with James McMahon who came to Glasgow in the
1820’s and married Mary Lynch there in 1828.  Steve McMahon, born
near Liverpool, played for Liverpool football club in the late 1980’s.

America.  Bernard McMahon,
driven to exile by the state of Irish politics. settled in Philadelphia
in 1802 and  made his name there in the cultivation of rare
plants.  Helped
by his Irish wife, he built up one of the biggest seed businesses in
the United States and had the evergreen shrub, Berberis mahonia, named
after him.

An earlier McMahon arrival from Ireland had been Richard McMahon
sometime in the 1740’s.  He had settled initially in Wilmington,
Delaware before moving onto Kentucky.  His son William Friend
senior was killed by Indians in Ohio in 1793.
His grandson William Friend junior was an itinerant Methodist preacher,
passing through Kentucky, Arkansas, and Louisiana before making it to
Texas in the 1820’s.

More McMahons came in the 19th century.  Among them were:

  • Martin McMahon from Waterford, who arrived in New York with his
    parents via
    Canada in the early 1840’s.  He was a Union army
    general during the Civil War and later a lawyer and US Marshal in New
  • William McMahon from Belfast, who came in the 1850’s to Wisconsin
    to raise pigs (however, his pigs were wiped out in an
    epidemic).  William fought on the Union side in the Civil
  • Patrick and Mary McMahon, who arrived after the Civil War and
    settled in Jersey City.  Patrick and his sons were
  • and James and Mary McMahon from Clare, who arrived in the 1860’s
    and headed west to Davenport, Iowa.

Edward McMahon came over from Ireland, probably in the 1880’s, and
settled in Lowell, Massachusetts.  His son Joseph started a
plumbing business and Joseph’s grandson was Ed McMahon, Johnny Carson’s
TV sidekick.
Then came the brothers Edward and James (Jess) McMahon from Galway to
New York in the early 1900’s.  Jess began promoting professional
wrestling matches in the New York area in the 1920’s.  He was the
forebear of three generations of famous McMahon wrestling promoters.

Canada.  Patrick McMahon,
a Catholic priest, had come out to Quebec in 1817, after having
completed his studies in county Laois.   He ministered to the
growing Catholic presence there until his death in 1851.
Also moving to Quebec from Laois was a recent widow, Ellen McMahon, and
her nine children in 1837.  They eventually came to live just
outside Toronto where two of her sons learnt the trade of coopering.

Patrick and Ellen McMahon from Limerick came to Canada in 1841 and
settled in Finch township, Ontario.

McMahon Miscellany

If you would like to read more, click on the miscellany page for
further stories and accounts:

Select McMahon Names

was the bandit who fought against the Anglo-Normans for
forty years and is seen as the forebear of the McMahons of Oriel.
Comte de MacMahon
, was
a Marshal of France and its President in
the 1870’s.
Jess McMahon was the American
founder in
1925 of World Wrestling Entertainment.
Billy McMahon was a
long-serving Australian minister and briefly, in 1971-2, Prime Minister.
Ed McMahon was Johnny Carson’s
sidekick on TV’s Tonight Show.

Select McMahons Today

  • 16,000 in the UK (most numerous
    in London)
  • 15,000 in America (most numerous in New York)
  • 29,000 elsewhere (most numerous in Ireland)




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