"You canker blossom!" 3 Shakespearean Insults
by 1942, noun and verb, "sneak off, escape," American English slang, probably from cop a plea (c.1925) "plead guilty to lesser charges," probably from northern British slang cop "to catch" (a scolding, etc.); cf. cop a feel "grope someone" (1930s); see cop (v.). Sense of "evade an issue or problem" is from 1960s.
1704, northern British dialect, "to seize, to catch," perhaps ultimately from Middle French caper "seize, to take," from Latin capere "to take" (see capable); or from Dutch kapen "to take," from Old Frisian capia "to buy," which is related to Old English ceapian (see cheap). Related: Copped; copping.
[origin uncertain; perhaps ultimately fr Latin capere ''seize,'' by way of French; police officer sense a shortening of copper; second sense ''seize, catch'' attested by 1704]
An evasion; an excuse for inaction: Arguing about standards is a ''cop-out'' (1960s+ Counterculture)