For other uses, see Casey (disambiguation) . Casey is a given name, derived either from the Irish Gaelic cathasaigh, meaning vigilant or watchful. or from a combination of the initials K.C.It is in use for both boys and girls in the United States, often with variant spellings.or other uses, see Casey (disambiguation) . Casey is a given name, derived either from the Irish Gaelic cathasaigh, meaning vigilant or watchful. or from a combination of the initials K.C.