Ó Murchadha or (modern) Ó Murchú - anglicised as Murphy and earlier as (O) Murchoe, Morchoe etc means ?sea warrior? in Irish. As Murphy it is the most numerous surname in Ireland, although there are more Murphys now in America than there are in Ireland.
Mac Murchaidh - also anglicised as Murphy. Woulfe in 'Sloinnte Gaedheal is Gall: Irish Names and Surnames' adds that this name is the Ulster variant of:
Mac Murchadha- a Leinster name and the 'tribe' of the infamous king of Leinster Dermot MacMurrough, who invited Strongbow and his Welsh-Norman mercenaries into Ireland, thus involving England in Irish history. The infamous Dermot's grandfather, Murchadha or Murrough, is the eponymous ancestor of the Wexford MacMurchadha, not of the Ó Murchadha sept who were also in Wexford. According to Woulfe (op. cit.) Dermot's descendants gave rise to the distinct surname Cavanagh or Kavanagh, through his son Domhnal Caobhánach.
There are several septs of Ó Murchadha recorded in counties Tyrone, Sligo and Wexford; the latter were a branch of the Uí Ceinseallaigh. It is probably this family who became very numerous. It is also likely that the Co Cork Murphys are a branch of this Wexford sept.
In William Petty's 1659 Census, the following are recorded:
Wexford town and liberties: Murphy (14 families); New Rosse: Murphy (10); Barony of Forth: O Morroe (27) Morrogh (19) Murphy (16); Bargie: O Morrow (6) Morrogh (5) Murphy (20); Shelmaleer: McMorrogh (6) Murphy (42); Bantry: Murchoe (18) Murphy (31); Ballaghkeene: Murchoe (24) Murphy (60); Goary: Murphy (25)
Cork city and liberties: Murphy (45) O Murraghow (8); Moyalle; O Morroghow (5); Barony of Kinalmeaky: O Morohow (11) Murphy (25); Killbrittaine: Murphy (19); Carberry West: Murphy (32); Beere and Bantry: Murphy (17); Barrymore: Murphy (44); Kilmore and Orrery: Murphy (18)
Kilkenny city and liberties: Morphey (12); Barony of Gowran: Morphy (118); Iverke: Morphey (6); Ida, Igrin and Ibercon (72); Knocktopher: Morphey (11); Fassagh Deinin: Murphy (16); Kells: Morphey (9); Skillellogher: Morphy (18); Crannagh: Morphy (12)
Oryer Barony: O Murphy (44); Lower Fewes: Murphy (7)
These are the main concentrations of Murphys in the 1659 Census. In Co Sligo a few McMurey(11) and McMorey(14) occur, otherwise there are no other names resembling. It is worth noting how the anglicisation 'Murphy' appears in the 1659 Census to be in the process of replacing the earlier forms of O Morroghow etc.
In Griffith's 'Primary Valuation' of Irish households between 1847 and 1860 most Murphy households were found in the counties Cork (2639 + 448 city) and Wexford (1688) followed by Kilkenny (888) Kerry (787) Armagh (468) and Tipperary (463). The total was 13539.
The 1890 Birth Registrations in Ireland, published in R.E. Matheson's 'Special Report...' (1894), show most Murphys in counties Cork (390), Wexford (137) and Dublin (132). The total number of births was 1385. It was the most numerous name in Cos Wexford, Carlow and Armagh, and the second most numerous in Co Cork. Murphy was classified as the most numerous name in all Ireland.
Two famous Murphys:
Father John Murphy D.D., acted as one of the leaders of the Wexford Rising in 1798: he was brutally put to death on the 26th June 1798.
William Martin Murphy founded the 'Irish Independent' newspaper in 1905. He was the aggressive leader of the anti- workers' employers association in the Dublin 'Lock-Out' of 1913.