1530s, "make thin, lean, slender, or rare; reduce in thickness or density" (the literal sense, now rare); from Latin extenuatus, past participle of extenuare "lessen, make small, reduce, diminish, detract from," from ex "out" (see ex-) + tenuare "make thin," from tenuis "thin," from PIE root *ten- "to stretch." Used over the years in a variety of literal and figurative senses in English. From 1560s as "to lessen, make smaller in degree or appearance, make less blamable, lower in importance or degree." Related: Extenuated; extenuating. Extenuating circumstances (1660s) are those which lessen the magnitude of guilt (opposed to aggravating).