latest adj.

Old English læt "occurring after the customary or expected time," originally "slow, sluggish, slack, lax, negligent," from Proto-Germanic *lata- (source also of Old Norse latr "sluggish, lazy," Middle Dutch, Old Saxon lat, Dutch laat, German laß "idle, weary," Gothic lats "weary, sluggish, lazy," latjan "to hinder"), from PIE *led- "slow, weary," from root *‌‌lē- "to let go, slacken."

From mid-13c. as "occurring in the latter part of a period of time." From c. 1400 as "being or occurring in the near, or not too distant, past; recent" (of late). From this comes the early 15c. sense "recently dead, not many years dead" (as in the late Mrs. Smith). Of menstruation, attested colloquially from 1962. Expression better late than never is attested from late 15c. As an adverb, from Old English late "slowly."

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.