CYA
Regarding "CYA", just a little more explanation may be in order for our friends from other countries or cultures. With thanks to our friends at
http://www.wordwizard.com --
This phrase was originally military and arose in the 1950s [probably during the Korean War]. It’s acronym, also widely used, is C.Y.A. This expression saw duty in Viet Nam and is commonly used in government, business, and elsewhere. Some more discrete folks in other lands (see below) use the bowdlerized version “cover one’s back.”
__________________________________________________________________________________
Cover means provide protection and in almost any old Western B-movie someone had to say something to the effect, “Cover me Zeke. I’m goin’ in.”
COVER transitive verb, Military: to protect and guard from attack (a soldier, force, or military position) during an expected period of ground combat by taking a position from which hostile troops can be fired upon. <units covering the retreat of the main army> <ships covering approaches to the harbor> <. . . just lawyers’ endless loopholes and cover-your-ass clauses> (Random House and Merriam-Webster’s Unabridged Dictionaries)
__________________________________________________________________________________
COVER ONE’S ASS/TAIL, slang (vulgar) [mid 1900s to present]. 1) verb phrase: to take measures that will prevent one from suffering blame, loss, harm, etc.; to protect oneself; to act in advance of some hazard to protect one’s interest; to provide or arrange for exculpation; devise excuses and alibis. Cf. C.Y.A. <Some call it ‘risk management,’ others ‘covering your ass’—Toronto Life> <The FBI may have to let you be destroyed to cover its own ass—Nat Hentoff> <CYA, you know, that old French expression that means making sure that when historians write about it all it wont be seen as happening on your shift—Washington Post>. 2) adjective phrase: <writing long cover-your-ass memos—Village Voice>. (Random House Unabridged Dictionary and Slang and Euphemism by Spears, Chapman’s Dictionary of American Slang)
COVER YOUR ASS/C.Y.A. or CYA, phrase [1950s and still in use] (originally U.S. military): 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. (Cassell’s Dictionary of Slang)
COVER ONE’S BACK (or North American ‘ass’), Informal: forsee and avoid the possibility of attack or criticism. (Oxford Dictionary of Idoms)