1834, from Latinized form of Greek eskhatos "last, furthest, uttermost, extreme, most remote" in time, space, degree (from PIE *eghs-ko-, suffixed form of *eghs "out;" see ex-) + -ology. In theology, the study of the four last things (death, judgment, heaven, hell). Related: Eschatological; eschatologically.
c. 1200, "last, final," superlative of late. From 1590s as "most recent." As a noun, 1520s, "the last in order." Colloquial the latest "the news" attested from 1886. At the latest "at the most distant date" is from 1884.
Old English todæge, to dæge "on (this) day," from to "at, on" (see to) + dæge, dative of dæg "day" (see day). Meaning "in modern times" is from c. 1300. As a noun from 1530s. Generally written as two words until 16c., after which it usually was written to-day until early 20c.
Similar constructions exist in other Germanic languages, such as Dutch van daag "from-day," Danish and Swedish i dag "in day." German heute is from Old High German hiutu, from Proto-Germanic *hiu tagu "on (this) day," with first element from PIE pronominal stem *ki-, represented by Latin cis "on this side."