cop

Uncertain. Perhaps from Middle English *coppen, *copen, from Old English copian (“to plunder; pillage; steal”); or possibly from Middle French caper (“to capture”), from Latin capiō (“to seize, grasp”); or possibly from Dutch kapen (“to seize, hijack”), from Old Frisian kāpia (“to buy”), whence West Frisian keapje, Saterland Frisian koopje, North Frisian koopi, kuupe. Compare also Middle English copen (“to buy”), from Middle Dutch copen.

Short for copper (“police officer”), itself from the verb cop (“to lay hold of”) above, in reference to arresting criminals. An erroneous folk etymology derives it from the acronym “Constable On Patrol” (C.O.P.).