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McMahon Family History
Mac Mathghamhna- anglicised MacMahon, McMahon, MacMann, Mahon & c. There seems little doubt that the root word is 'mathghamhan' -'bear' or 'bear-calf', and used as an epithet, which was popular among the O Briens in later medieval Ireland.
In Litriú nua the spelling is Mac Mathúna.
Perhaps the most important of the two major septs of this name was that of Thomond, who took their name from Mathgamain, grandson of Brian Boru. Mathgamain'ss father was Muirchetach Mór ua Briain, king of Ireland (1094-1119). Their territory was that of Corca Bhaiscinn in South West Clare. They became numerous in their homeland, and by the end of the 19th century their name had become the most numerous surname in Co Clare.
One tragic note is the death of their last chief in 1602, at the battle of Kinsale, killed, it is said, accidentally by his own son.
The other, entirely distinct, sept is that of Orghialla (Oriel). These MacMahons ruled the ancient territory of that name from the the 13th to the late 16th century. Oriel comprised modern Cos Armagh and Monaghan, and adjacent areas in Down, Louth and Fermanagh. In spite of the ruthless English expugnatio of clan holdings, they retained considerable influence, until Cromwellian times, in Co Monaghan.
By the time of the 'Census' of Sir William Petty in 1659, McMahon is listed as a 'Principal Irish Name' in:
Tulla Barony, McMahon 12 (families); Island Barony, McMahon 15 (also McMahony 4: possibly the entirely distinct name O Mahony, which is lexically cognate); Moyferta, McMahon 9 (Mahony is mentioned separately in this barony, with 12).
Therlach McMahon of Kilrush appears in this last barony on the list of 'tituladoes' or 'gentlemen', among several others with native names. Many 'tituladoes', or gentlemen of property and standing, in the 'Census', further east in Ireland would be planters/settlers. Likewise, Mortagh McMahon in Kilmacduane parish, is described as a titulado or 'gentleman'.
Still in Co Clare, in the barony of Ibrickayne & borough of Enish (Ennis) Mahon/MacMahon is represented by 8 families.
For the Oriel sept:
listed as a 'Principal Irish Name', under the county name, are 112 families of McMaghone. Interestingly, the names of the 'tituladoes' appear largely to be of planter stock.
Clownish Parish & c. McMahon, 30 families; Dummully Parish & c. McMahon, 8 families.
Lowth Barony, McMahon 20 (families); Dundalk Barony, McMahon 10; Farrard, McMaughon 5; Atherdee, McMaughon.
Griffith's 'Valuation' of property in the 1850s, listed most McMahon households in counties: Clare 799, Monaghan 436, Limerick 212 (+city 61), Fermanagh 134 and Cavan 116.
The 1890 births registrations, report most McMahons in counties Clare, Monaghan, Limerick and Dublin.
Some famous McMahons:
Maurice MacMahon, Lord of Moguien in Burgundy, France, and brother of John B. MacMahon, Marquis d'Éguilly (born in Limerick in 1715), was a captain in the Jacobite army of Bonny Prince Charlie in 1745/46. These brothers came from the Clare sept.
Hugh MacMahon (1660-1737), and his nephews Bernard and Ross Roe, were all archbishops of Armagh during the difficult penal times of the early 18th century. Hugh's mother, Eibhlin O Reilly, was the daughter of Colonel Philip O Reilly, a leader of the 1641 Rebellion. This MacMahon family were of the Oriel MacMahons.