Why Are American Policemen Called Cops?

Although American police departments were formed after a study of the British police system, American policemen did not inherit the British nickname for their officers. Instead, American policemen became known as "cops" or "coppers."

There are two theories as to how these names came about.

Some say that because New York policemen once wore an 8-pointed copper star on their uniforms, the name "copper" was given to them. Other people say that "cop" came from the first letters of the description of the policemen, "Constable On Patrol."