copper

Copper comes from Middle English coper, from Old English coper/copor, from Late Latin cuprum — a shortening of Latin aes Cyprium, "Cyprian metal," naming Cyprus as a major Bronze Age source of copper. The island's own name is traced back to a Northwest Semitic goddess linked to a root meaning "great" or "large."

The word simply tracked the metal itself, moving from Greek to Latin to Old English to Middle English with its meaning intact — copper ore, copper metal, and even bronze in earlier use.

It's a doublet of kobo, sharing the same deep root. Curiously, the slang word for a police officer — also spelled 'copper' — is a completely separate word, probably built from cop ("to arrest") plus the agent suffix -er, not from the metal at all.