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).