Source: O’CONNOR People and Places, by Hugh W.L. Weir
The name O’Conor or O’Connor is one of the most numerous and most distinguished in Ireland. But not all who call themselves such are descended from the same source, nor are they of the same clan. There are, in fact, at least three main groups, who are each descended from a different Conor or Connor, a first name which was once particularly common. Possibly the most popular and best know O’Conors (they usually use this spelling) are those of Connacht (to whom also belonged the last Kings of Ireland), the north-western Province; the others being Munster, Leinster, Ulster and Royal Meath. They are the descendants of Conchobhar (the helping warrior), son of Teige and descendant of Heremon who was reputedly the seventh son of King Milesius of Spain, and of Ireland, whose mother Creassa’s sister was the mother of King Brian Boru (from whom descend the O’Briens). Hence the name O’Connor, descendant of Conor (Conchobhar in Irish). Connected with them are the Septs of O’Conor Roe and O’Conor Sligo. Another great O’Connor family is that based in the Irish midlands, the O’Connors, Princes of Offaly who descend from, amongst other distinguished royal personages, Finn Mac Coole, the third century leader of the Fianna (Fenians) who gave forty-four kings to the Kerry area between the Maine and the Shannon rivers. The O’Connors, Kings of Kerry, descend from another of Milesius’ sons, Ir. His descendant, whose grandson Corc died in 1019, was also Conchobhar. They based themselves eventually at Carrigafoyle on the Shannon in North Kerry. Other bearers of the name include the O’Connors of Moy Ith around Raphoe in Co. Donegal, the O’Connors of Corcumruadh in Co. Clare, and the O’Connors of Orgiall in Ulster (also known as Clan Colla).