Green’s Dictionary of Slang

(orig. US milit.) a phr. meaning look after yourself before worrying about anyone else, be it colleagues, customers, the larger world, whatever; the basic admonition to anyone, at any level, working in government or a large corporation.

1959		W.A. Heflin Aerospace Gloss. n.p.: CYA (abbr.) ‘Keep your skirts clean.’ Pentagon slang.
1970		G. Scott-Heron Vulture (1996) x: That read like [...] a bit of C.H.A. by the Dean. (In traditional institutions when someone makes a request for extraordinary consideration the person responsible for approval likes to ‘cover his ass.’).
1982		(con. 1970) J.M. Del Vecchio 13th Valley (1983) 464: Uncle Tony said CYA – you’d understand.
1989		H. Rawson Dict. of Invective (1991) 27: cover [one’s] ass, to. To protect oneself, especially in a bureaucratic setting, often abbreviated C.Y.A., for Cover Your Ass.
1994		Mollen Report 59: I guess you would say it was an 'Us against Them' theme. . . . [T]hat was one of the terms used in the Academy, ‘CYA’.
2004		Laugh at Liberals 22 Mar. 🌐 Folks, you are witnessing some major league C.Y.A. taking place.