When someone is called K.C. it is usually initials for a first and middle name.
The name Casey, however, can be found in this database:
CASEY m,f English Pronounced: KAY-see From the Irish surname Ó Cathasaigh, which means "descendent of Cathasaigh". The name Cathasaigh means "vigilant" in Gaelic. Casey also serves as a form of CASS (feminine).