cantharides (n.)

late 14c., cantaride, type of beetle (the "Spanish fly"), especially as dried, ground up, and used medicinally to raise blisters, from Latin plural of cantharis, from Greek kantharis "blister-fly, a kind of beetle." Beekes says this is a derivative of kantharos, also the name of a kind of beetle, for which there is no good etymology. Their use (taken internally) as a sexual stimulant is attested by c. 1600. Related: Cantharic.