1570s, via Fr., from It. complimento "expression of respect and civility," from V.L. *complire, for L. complere "to complete," via notion of "complete the obligations of politeness." Same word as complement but by a different etymological route; differentiated by spelling after 1650.
1419, "that which completes," from O.Fr. complement, from L. complementum "that which fills up or completes," from complere "fill up" (see complete). Originally also having senses which were taken up c.1655-1725 by compliment (q.v.).
c.1300, "negotiate, bargain, deal with," from O.Fr. traitier (12c.), from L. tractare "manage, handle, deal with," originally "drag about," frequentative of trahere (pp. tractus) "to pull, draw" (see tract (1)). Meaning "to entertain with food and drink by way of compliment or kindness (or bribery)" is recorded from c.1500. Sense of "deal with in speech or writing" (early 14c.) led to the use in medicine (1781), "to attempt to heal or cure." The noun is first recorded late 14c., "action of discussing terms;" sense of "a treating with food and drink" (1650s) was extended by 1770 to "anything that gives pleasure." Treatment "conduct, behavior" is recorded from c.1560; in the medical sense, it is first recorded 1744.
c.1200, from Kentish form of O.E. lyft- "weak, foolish" (cf. lyft-adl "lameness, paralysis," E.Fris. luf, Du. dial. loof "weak, worthless"). It emerged 13c. as "opposite of right," a derived sense also found in M.Du., Low Ger. luchter, luft. Ger. link, Du. linker "left" are from O.H.G. slinc, M.Du. slink "left," related to O.E. slincan "crawl," Sw. linka "limp," slinka "dangle." Replaced O.E. winestra, lit. "friendlier," a euphemism used superstitiously to avoid invoking the unlucky forces connected with the left side (see sinister). The Kentish word itself may have been originally a taboo replacement, if instead it represents PIE root *laiwo-, meaning "considered conspicuous" (represented in Gk. laios, Latvian laevus, and Rus. levyi). Gk. also uses a euphemism for "left," aristeros "the better one" (cf. also Avestan vairyastara- "to the left," from vairya- "desirable"). But Lith. kairys "left" and Lettish kreilis "left hand" derive from a root that yields words for "twisted, crooked." Political sense arose from members of a legislative body assigned to the left side of a chamber, first attested in Eng. 1837 (by Carlyle, in ref. to the Fr. Revolution), probably a loan-translation of Fr. la gauche (1791), said to have originated during the seating of the Fr. National Assembly in 1789 in which the nobility took the seats on the President's right and left the Third Estate to sit on the left. Became general in U.S. and British political speech c.1900 (cf. Leftist, 1924; left wing, 1898). Used since at least 1612 in various senses of "irregular, illicit," such as the phrase left-handed compliment (1881). Phrase out in left field "unorthodox, unexpected" is attested from 1959. Lefty "left-handed person" is 1886, Amer.Eng., baseball slang. The Left Bank of Paris has been associated with intellectual and artistic culture since at least 1893.