mid-14c., "change the form of" (transitive), from Old French transformer (14c.), from Latin transformare "change in shape, metamorphose," from trans "across, beyond" (see trans-) + formare "to form" (see form (v.)). Intransitive sense "undergo a change of form" is from 1590s. Related: Transformed; transforming.
early 15c., "to bend inward," from Latin inflectere (past participle inflexus) "to bend in, bow, curve," figuratively, "to change, alter, influence," from in- "in" (see in- (1)) + flectere "to bend" (see flexible). Grammatical sense "to vary by change of form" (especially at the end of a word) is from 1660s. Related: Inflected; inflecting.
The meaning "device for changing the direction of something or making or breaking a connection" is first recorded 1797. "The peg sense suits the mech(anical) applications" [Weekley]; also compare switchblade. These senses in English might be a direct borrowing from those senses in Continental Germanic languages rather than a continuation of the "pliant wand" sense. The meaning "a change from one to another, a reversal, an exchange, a substitution" is first recorded 1920; extended form switcheroo is by 1933.
late 14c., alteracioun, "change, transformation, action of altering," from Old French alteracion "change, alteration" (14c.), and directly from Medieval Latin alterationem (nominative alteratio), noun of action from past-participle stem of Late Latin alterare "to change," from Latin alter "the other (of the two)," from PIE root *al- (1) "beyond" + comparative suffix -ter (as in other). Meaning "change in character or appearance" is from 1530s; that of "change in ready-made clothes to suit a customer's specifications" is from 1901. Related: Alterations.
also moult, c. 1400, mouten, of feathers, hair, etc., "to be shed, fall out," from Old English *mutian "to change" (in bemutian "to exchange"), from Latin mutare "to change" (from PIE root *mei- (1) "to change"). Transitive sense, "to shed or cast (feathers, fur, skin)" is by mid-15c. With unetymological -l-, late 16c., on model of fault, etc. Related: Molted, moulted; molting, moulting. As a noun, "act or process of shedding an outer structure or appendage," from 1815.
late 14c., "to change (something), make different in some way," from Old French alterer "to change, alter," from Medieval Latin alterare "to change," from Latin alter "the other (of the two)," from PIE root *al- (1) "beyond" + comparative suffix -ter (as in other). Intransitive sense "to become otherwise" first recorded 1580s. Related: Altered; altering.