Word Origin & History
late 13c., "two of a kind, coupled in use," from O.Fr. paire, from L. paria "equals," neut. pl. of par (gen. paris) "a pair, counterpart, equal," noun use of par (adj.) "equal," of unknown origin, perhaps connected with *per-, PIE root meaning "to sell, buy" (on notion of "give equal value for"), which
would connect it with L. pretium "price," Lith. perku "I buy," Gk. porne "prostitute," lit. "bought, purchased." Or from PIE *pere- "to grant, allot" (which would connect it with part and portion). The verb, "to mate" is first attested 1611 in Shakespeare ("Winter's Tale"); sense of "to make a pair by matching" is from 1613; these often are distinguished now by pair off (c.1803) for the former and pair up (1908) for the latter. Pair bond (v.) is first attested 1940, in ref. to birds mating.