Temperament
late Middle English: from Latin temperamentum ‘correct mixture’, from temperare ‘mingle’. In early use the word was synonymous with the noun temper.
wiktionary
Borrowed from Middle French tempérament, from Latin temperamentum.
etymonline
temperament (n.)
late 14c., "proportioned mixture of elements," from Latin temperamentum "proper mixture, a mixing in due proportion," from temperare "to mix in due proportion, modify, blend; restrain oneself" (see temper (v.)). In old medicine, it meant a combination of qualities (hot, cold, moist, dry) that determined the nature of an organism; thus also "a combination of the four humors (sanguine, choleric, phlegmatic, and melancholic) that made up a person's characteristic disposition." General sense of "habit of mind, natural disposition" is from 1821.
