Ó Cathail

Cahill (locally /ˈkɑːhɪl/, UK: /ˈkɑːhɪl/ or /ˈkeɪhɪl/) is a name of Irish origin. It is the anglicised version of the Gaelic "Ó Cathail" meaning "descendant of Cathal". "Cathal" consists of two parts: "cath" means battle; the second could be "val" (rule), so that the name as a whole meant "battle ruler" or "strong in battle", or it could be "all" (great), so that the name as a whole meant "great warrior". Notable people with the surname include:

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Wikipedia