plastron n.

also piastre, 1620s, "Spanish dollar, piece of eight," also used as the name of a monetary unit and coin of Turkey (1610s, in Turkish called ghurush, but originally debased Spanish dollars), from French piastre, from Italian piastra "thin metal plate," short for impiastro "plaster," from Latin emplastrum, from Greek emplastron (see plaster (n.)). The Italian word was applied to the Spanish silver peso, later to the Turkish coin based on it. Compare shinplaster.