late 14c., "ending, determining, conclusive," from Old French definitif (12c.), from Latin definitivus "explanatory, definitive," in Late Latin "definite," from definit-, past-participle stem of definire "to limit, determine, explain," from de "completely" (see de-) + finire "to bound, limit," from finis "boundary, end" (see finish (v.)). As a noun, in grammar, "a defining or limiting word," by 1751. Related: Definitively; definitiveness.
c. 1500, "fixed, established; certain, precise;" 1550s, "having fixed limits," from Latin definitus "defined, bounded, limited," past participle of definire "to limit, determine, explain," from de "completely" (see de-) + finire "to bound, limit," from finis "boundary, end" (see finish (v.)). From 1727 in grammar, "defining, limiting." Definite means "defined, clear, precise, unmistakable;" definitive means "having the character of finality." Related: Definiteness.
1610s, "occurring at the end," from French conclusif, from Late Latin conclusivus, from conclus-, past participle stem of Latin concludere "to shut up, enclose," from assimilated form of com "together" (see con-) + -cludere, combining form of claudere "to shut" (see close (v.)). Meaning "definitive, decisive, convincing, being so forcible as not to admit of contradiction" (on the notion of "leading to a logical conclusion," and thus putting an end to debate) is from 1640s. Related: Conclusiveness.
"amorous trifling; giddy behavior," 1718, noun of action from flirt (v.) as though Latin. The date, alas, gives the lie to Chesterfield's charming story of its coinage (in The World, Dec. 5, 1754) but not his refinement of the definition: "[F]lirtation is short of coquetry, and intimates only the first hints of approximation, which subsequent coquetry may reduce to those preliminary articles, that commonly end in a definitive treaty."
c. 1200, "latest, final, following all others," a contraction of Old English latost (adj.) "slowest, latest," superlative of læt (see late); in some uses from late (adv.). Cognate with Old Frisian lest, Dutch laatst, Old High German laggost, German letzt.
Meaning "last in space, furthest, most remote" is from late 14c.; meaning "most unlikely or unsuitable" is from mid-15c. Meaning "most recent, next before the present" (as in last night, last September) is from late 14c.; latest would be more correct, but idiom rules and the last time I saw her might mean the most recent time this hour or the final time forever.
The biblical last days ("belonging to the end") is attested from late 14c. Last hurrah is from the title of Edwin O'Connor's 1956 novel. Last word "final, definitive statement" is from 1650s. A dying person's last words so called by 1740. As an adjective, last-minute attested from 1913. Last-chance (adj.) is from 1962. Expression if it's the last thing I do, expressing strong determination, is attested by 1905.