An Etymological Dictionary of the German Language/Kupfer
Kupfer, n., ‘copper,’ from the equiv. MidHG. kupfer, OHG. chupfar, n.; an old loan-word from which *kuppor must have been the earliest form; the word was borrowed before the 7th cent.; comp. Du. and MidLG. koper, AS. copor, E. copper, Scand. kopar. These are probably based on MidLat. cuper (gen. -eris). Late Lat. cuprum, or rather œs cyprium, or simply cyprium (whence Fr. cuivre), is an Italian (not a Greek) term; the Teuts. probably owe to the Italians their earliest knowledge of copper. The island of Cyprus was called Kipper by the Germans of the Middle Ages, following the Byzant. and ModGr. pronunciation of Κύπρος; hence MidHG. kippor or kipperwîn, ‘Cyprian wine.’