Tempered
Old English temprian ‘bring something into the required condition by mixing it with something else’, from Latin temperare ‘mingle, restrain’. Sense development was probably influenced by Old French temprer ‘to temper, moderate’. The noun originally denoted a proportionate mixture of elements or qualities, also the combination of the four bodily humours, believed in medieval times to be the basis of temperament, hence temper (sense 1 of the noun) (late Middle English). Compare with temperament.
wiktionary
From Middle English tempred, itempered, ytempred, ytemprid, from Old English ġetemprod(“tempered, moderate, goverened, cured”), past participle of Old English ġetemprian(“to temper, moderate, govern, cure”), equivalent to temper + -ed.
Partly from Middle English temperd, temprede, from Old English temprode, first and third person singular preterit of Old English temprian; and partly from Middle English tempred, i-tempred, from Old English ġetemprod. Equivalent to temper + -ed.
etymonline
tempered (adj.)
1650s, "brought to desired hardness" (of metals, especially steel), past-participle adjective from temper (v.). Meaning "toned down by admixture" is from 1650s; of music or musical instruments, "tuned," from 1727.
