The term Copper was the original, unshortened word, originally used in Britain to mean "someone who captures". (In British English the term Cop is recorded (Shorter Oxford Dictionary) in the sense of 'To Capture' from 1704, derived from the Latin 'Capere' via the Old French 'Caper'). The common myth is that it's a term referring to the police officer's buttons which are made of copper.

I couldn’t care less (but one must keep up appearances, right?)

another slang word for police

A slang term used for police officers.
see also pig,50
the term "coppers" can be traced back tot he early 19th century in new york city when the first police force consisting of an 8 men unarmed patrol unit wore on their shirt an 8 point copper badge to distinguish themselves as officers of the law. as a result the general public started calling them coppers

Term used by gangsters in the 20's and 30's for a police officer.

(Mainly Brit.)

A term used for spare or loose change.

term used for police officers in the 20's and 30's because of the copper buttons they used to have on their uniforms