Origin and history of temperate

"mix or work up into proper condition, adjust or restore to proper proportions;" Middle English temperen, from late Old English temprian "to moderate by mixture, bring to a proper or suitable state, modify (some excessive quality), restrain within due limits," from Latin temperare "observe proper measure, be moderate, restrain oneself," also transitive, "mix correctly, mix in due proportion; regulate, rule, govern, manage."

This often is described as from Latin tempus "time, season" (see temporal (adj.1)), with a notion of "proper time or season." But as the root sense of tempus seems to be "stretch," the words in the "restrain, modify" sense might be from a semantic shift from "stretching" to "measuring" (compare temple (n.1)).

The meaning "make (steel) hard and elastic" is from late 14c. The sense of "tune the pitch of a musical instrument" is recorded from c. 1300. Related: Tempered; tempering.

c. 1400, "intemperate, given to sudden outbursts," from un- (1) "not" + temperate (adj.). By 1610s as "addicted to drink."