Ó Maolchatha
Ó MAOLCHATHA, Ó MAOLCHATHAIGH—I—O Mulcaha, O Mulcahy, Mulcahy; 'descendant of Maolchatha' (battle-chief), or 'Maolcathach' (warlike chief), or 'Maolchathaigh' (follower of Cathach, warlike); a well-known Munster surname. It seems to have originated in South Tipperary, but is now common also in Waterford, Cork and Limerick.
Alphabetical Index to Irish Surnames