Donnelly is an Irish surname. It is the Anglicized form of the Gaelic "Ó Donnghaile", "Ó" meaning male descendant of, and Donnghaile, a personal name composed of the elements "donn" (brown), plus "gal" (valour). The name O’Donnelly is derived from the descendants of Donnghaile (Donnghal) who was the great grandson of Domhnall, King of Aileach. Early ancestors of this surname were a part of Cenél nEoghain and the Uí Néill as descendants from the line of Eógan mac Néill one of the seven sons of Niall Noígíallach.
