Ó Fionnghalaigh
Ó FIONNGHALAIGH—I—O Fynnola, O Fenellie, Finnelly, Fennelly, Finley, Fenley, Finlay, Findley, &c.; 'descendant of Fionnghalach' (fair-valorous, derivative of Fionnghal); also written Ó Fianghalaigh, and, by the aspiration of the initial f, changed to Ó hIonnghalaigh, which see; the name of an Ormond family, doubtless descended from Fionnghalach, son of Donnchuan, one of the leaders of Brian Boru's hosts at Clontarf.
Alphabetical Index to Irish Surnames