A surname, most commonly of Irish origin, possibly meaning 'combat' or related to a place name.
From Irish 'Ó Cathail' meaning 'descendant of Cathal', where 'Cathal' possibly derives from 'cath' (battle/combat) and 'gal' (valor). The Anglicized spelling became 'Cahill'.
Irish surnames beginning with 'Ó' or 'Mac' are genealogical records—'Cahill' from 'Ó Cathail' literally means you're descended from someone named Cathal, and that tradition of preserving family lineage in surnames is unique to Celtic cultures.
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