asbestos

1650s, earlier albeston, abestus (c.1100), name of a fabulous stone, which, set afire, could not be extinguished; from Old French abeste, abestos, from Latin asbestos "quicklime" (which "burns" when cold water is poured on it), from Greek asbestos, literally "inextinguishable," from a- "not" (see a- (3)) + sbestos, verbal adjective from sbennynai "to quench," from PIE root *(s)gwes- "to quench, extinguish" (cf. Lithuanian gestu "to go out," Old Church Slavonic gaso, Hittite kishtari "is being put out").

The Greek word was used by Dioscorides as a noun meaning "quicklime." "Erroneously applied by Pliny to an incombustible fibre, which he believed to be vegetable, but which was really the amiantos of the Greeks" [OED]. Meaning "mineral capable of being woven into incombustible fabric" is from c.1600 in English; earlier this was called amiant (early 15c.), from Latin amiantus, from Greek amiantos, literally "undefiled" (so called because it showed no mark or stain when thrown into fire). Supposed in the Middle Ages to be salamanders' wool. Prester John, the Emperor of India, and Pope Alexander III were said to have had robes or tunics made of it.