Almost undoubtedly from Carlow, Wexford or Wicklow, in Leinster, South East Ireland, the home of all Cavanaghs and Kavanaghs the original family of the Kings of Leinster.

Kavanagh is one of the very few ancient Gaelic Irish surnames which has neither the prefix Mac or O. In Irish it is simply Caomhanach which is an adjective denoting association with Caomhan, in this case St. Caomhan, the first Kavanagh having been fostered by a successor of that saint. It was not customary for such epithets to be perpetuated, as happened with this branch of the MacMurroughs. The first Kavanagh was Donal son of Dermot MacMurrough, King of Leinster, who was one one of the prominent figures in Irish history, being the immediate cause of the Anglo-Norman invasion. The Kavanagh territory lay then in Counties Wexford and Carlow and they continued to be extensive landowners there up to recent times. The name is very numerous in and around Co. Wexford in all classes of society, so much so indeed that they are enough Kavanaghs in the south-eastern counties of Leinster by themselves, without counting the scattered Kavanaghs in the rest of the country, to put the name in the list of the eighty commonest surnames in the country: all told they hold fifty-third place in that list.