Ó hAilgheanáin
Ó hAILGHEANÁIN—I—O Hallinaine, O'Hallinan, Hallinan, Hallanan, Halnan; 'descendant of Ailgheanán' (diminutive of ailghean, noble offspring); an old Munster surname, found chiefly in Cork and Limerick; also apparently a Connacht surname, now not uncommon in West Mayo. MacBeathaidh Ó hAilgheanáin was Bishop of Cork at the beginning of the 12th century.
Alphabetical Index to Irish Surnames