mid-15c., "fact of being tempered, proper proportion;" 1530s, "character or nature of a substance," from Latin temperatura "a tempering, moderation," from temperatus, past participle of temperare "to be moderate; to mingle in due proportion" (see temper, v.). Sense of "degree of heat or cold" first recorded 1670 (Boyle), from Latin temperatura, used in this sense by Galileo. Meaning "fever, high temperature" is attested from 1898.