early 15c., "to bend inward," from Latin inflectere (past participle inflexus) "to bend in, bow, curve," figuratively, "to change," from in- "in" (see in- (1)) + flectere "to bend" (see flexible). Grammatical sense is attested 1660s; pronunciation sense (in inflection) is c. 1600. Related: Inflected; inflecting.
