copper (n.1)
malleable metallic element, Old English coper, from Proto-Germanic *kupar (cognates: Middle Dutch koper, Old Norse koparr, Old High German kupfar), from Late Latin cuprum, contraction of Latin Cyprium (aes) "Cyprian (metal)," after Greek Kyprios "Cyprus" (see Cyprus).

Latin aes originally was "copper," but this was extended to its alloy with tin, bronze, and as this was far more extensively used than pure copper, the word's primary sense shifted to the alloy and a new word evolved for "copper," from the Latin form of the name of the island of Cyprus, where copper was mined. Aes passed into Germanic (which originally did not distinguish copper from its alloys) and became English ore. In Latin, aes was the common word for "cash, coin, debt, wages" in many figurative expressions. Chemical symbol Cu is from cuprum.
copper (n.2)
"policeman," 1846; agent noun from cop (v.).