turquoise n.

greenish-blue precious stone, 1560s, from French, replacing Middle English turkeis, turtogis (late 14c.), from Old French fem. adjective turqueise "Turkish," in pierre turqueise "Turkish stone," so called because it was first brought to Europe from Turkestan or some other Turkish dominion. Cognate with Spanish turquesa, Medieval Latin (lapis) turchesius, Middle Dutch turcoys, German türkis, Swedish turkos. As an adjective, 1570s. As a color name, attested from 1853. "Chemically it is a hydrated phosphate of aluminum and copper" [Flood].