Q From Billyboy Mackey: Could you possibly tell me the origin of the slang term for policemen, cops?
A Half a dozen explanations at least have been put forward for this one, including an acronym from “constable on patrol”, which is reminiscent of the story behind posh and quite certainly just as spurious. It is also said to come from the copper badges carried by New York City’s first police sergeants (patrolmen were alleged to have had brass ones and senior officers silver); it is almost as often said to refer to the supposedly copper buttons of the first London police force of the 1820s. Both these stories seem about equally unlikely.
The most probable explanation is that it comes from the slang verb cop, meaning “to seize”, originally a dialect term of northern England which by the beginning of the nineteenth century was known throughout the country. This can be followed back through the French caper to the Latin capere, “to seize, take”, from which we also get our capture.
The situation is complicated because there are — or have been — a number of other slang meanings for cop, including “to give somebody a blow”, and the phrase cop out, as an escape or retreat. Both of these may come from the Latin capere. But it’s suggested that another sense of cop, “to steal”, could come from the Dutch kapen, “to take or steal”. There’s also “to beware, take care”, an Anglo-Indian term from the Portuguese coprador, and phrases like “you’ll cop it!” (“you’ll be punished, you’ll get into trouble”), which could come from the idea of seizing or catching, but may be a variant of catch.
But the “seize; capture” origin for the police sense seems most plausible. So policemen are just those who catch or apprehend criminals, a worthy occupation. And a copper is someone who seizes, a usage first recorded in Britain in 1846.