Calorie
mid 19th century: from French, from Latin calor ‘heat’ + French suffix -ie (see -y3).
wiktionary
Borrowed from French calorie, formed from Latin calor.
etymonline
calorie (n.)
unit of heat in physics, 1866, from French calorie, from Latin calor (genitive caloris) "heat," from PIE *kle-os-, suffixed form of root *kele- (1) "warm."
As a unit of energy, defined as "heat required to raise 1 gram of water 1 degree Celsius" (the small or gram calorie), but as a measure of the energy-producing value of food, "heat required to raise 1 kilogram of water 1 degree Celsius" (the large calorie or kilocalorie). In part because of this confused definition, it was largely replaced 1950 in scientific use by the joule. Calorie-counting or -watching as a method of scientific weight-regulation is attested by 1908.
