distemper (v.)
mid-14c., "to disturb," from Old French destemprer, from Medieval Latin distemperare "vex, make ill," literally "upset the proper balance (of bodily humors)," from dis- "un-, not" (see dis-) + Latin temperare "mingle in the proper proportion" (see temper (v.)). Related: Distempered.
distemper (n.)
1550s, from distemper (v.); in reference to a disease of dogs, from 1747.