late 14c., eschaunge, "act of reciprocal giving and receiving," from Anglo-French eschaunge, Old French eschange (Modern French échange), from Late Latin excambium, from excambiare, from Latin ex "out" (see ex-) + cambire "barter" (see change (v.)). The practice of merchants or lenders meeting at certain places to exchange bills of debt led to the meaning "building for mercantile business" (1580s).
late 15c. (Caxton), in commerce, "to part with in return for some equivalent, transfer for a recompense, barter," from Old French eschangier "exchange, barter" (Modern French échanger), from Vulgar Latin *excambiare (source of Italian scambiare); see exchange (n.). Non-commercial sense of "to give and receive reciprocally" is from c. 1600. Related: Exchanged; exchanging.
1570s, "existing on both sides, exclusive or interchangeable" (of duties, etc.), with -al (1) + stem of Latin reciprocus "returning the same way, alternating," from pre-Latin *reco-proco-, from *recus (from re- "back;" see re-, + -cus, adjective formation) + *procus (from pro- "forward," see pro-, + -cus). Related: Reciprocally.
From 1590s as "given, felt, or shown in return;" c. 1600 as "corresponding or answering to each other, mutually equivalent." The sense of "moving backward and forward, having an alternating back and forth motion" (c. 1600) is obsolete. The noun meaning "that which is reciprocal" (to another) is from 1560s. In scientific and mechanical uses, reciprocating, reciprocative (1804), and reciprocatory (1826) have been tried.
"act of alternating; state of being alternate," mid-15c., alternacioun, from Old French alternacion "alternation," from Latin alternationem (nominative alternatio) "an interchanging," noun of action from past-participle stem of alternare "to do first one thing then the other; exchange parts," from alternus "one after the other, alternate, in turns, reciprocal," from alter "the other" (see alter).
"following each other by turns, reciprocal," 1510s, from Latin alternatus "one after the other," past participle of alternare "to do first one thing then the other; exchange parts," from alternus "one after the other, alternate, in turns, reciprocal," from alter "the other" (see alter).
Alternate means "by turns;" alternative means "offering a choice." Both imply two kinds or things. Alternation is the process of two things following one another regularly by turns (as night and day); an alternative is a choice of two things, the acceptance of one implying the rejection of the other. Related: Alternacy.