Ó hAilleagáin
Ó hAILLEAGÁIN—I—O Hallegane, O Hallagan, Halligan, Hilligan; 'descendant of Ailleagán' (diminutive of Áille, handsome, beautiful); also Ó hAllagáin; an old Ulster surname; now common also in Mayo and Roscommon.
Alphabetical Index to Irish Surnames