copper [OE] The verb cop [E18th], meaning ‘to catch’, comes from a northern English dialect word cap meaning ‘to capture or arrest’. This probably goes back to Latin capere, ‘to take or seize’. So a copper was a catcher, which is why it became an informal word for a police officer in the 1840s. Apprehended villains have been saying ‘it’s a fair cop!’ since the 1880s. See also capable. Copper, the reddish-brown metal, comes from Latin cyprium aes ‘Cyprus metal’. The island of Cyprus was the Romans’ main source of copper.