- calorie
- 1866, from L. calor (gen. caloris) "heat," from PIE *kle-os-, suffixed form of base *kele- "warm" (cf. L. calidus "warm," calere "be hot;" Skt. carad- "harvest," lit. "hot time;" Lith. silti "become warm," silus "August;" O.N. hlær, O.E. hleow "warm"). Technically, the heat required to raise 1 kilogram of water 1 degree Celsius. In scientific use, largely replaced 1950 by the joule. Caloric, the supposed elastic fluid that accounted for phenomena of heat in Lavoisier's now-abandoned theory, was in use from 1792.