The most commonly heard theories trace "cop" or "copper" meaning "police" to copper buttons worn on early police uniforms, or to copper police badges supposedly issued in some cities, but there is no convincing evidence for any of this. Still other theories explain "cop" as an acronym, standing for "Constable On Patrol," "Chief of Police" or other such phrases. But these "acronym" theories bear all the hallmarks of being spurious after-the-fact explanations invented to explain "cop." Among other sticky details is the fact that acronyms were virtually unknown in English before the 20th century, while "cop" itself was well established by the mid-19th century.To cut to the chase, the police sense of "copper" and "cop" probably comes originally from the Latin word "capere," meaning "to seize," which also gave us "capture." "Cop" as a slang term meaning "to catch, snatch or grab" appeared in English in the 18th century, ironically originally used among thieves -- a "copper" was a street thief. But by the middle of the 19th century, criminals apprehended by the police were said to have themselves been "copped" - caught - by the "coppers" or "cops." And there you have the etiology of "cop." Case, as the cops say, closed.