Casey \c(a)-sey\ as a boy's name (also used as girl's name Casey), is pronounced KAY-see. It is of Irish and Gaelic origin, and the meaning of Casey is "alert, watchful". From the male Gaelic name Cathasaigh. Also possibly a short form of Casimir. Made famous by the song about the engineer of the Cannonball Express train, Casey Jones. Baseball personality Casy Stengel; radio disc jockey Casey Kasem; actor Casey Affleck.