Etymology
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soon (adv.)
Old English sona "at once, immediately, directly, forthwith," from Proto-Germanic *sæno (source also of Old Frisian son, Old Saxon sana, Old High German san, Gothic suns "soon"). Sense softened early Middle English to "within a short time" (compare anon, just (adv.)). American English. Sooner for "Oklahoma native" is 1930 (earlier "one who acts prematurely," 1889), from the 1889 opening to whites of what was then part of Indian Territory, when many would-be settlers sneaked onto public land and staked their claims "sooner" than the legal date and time.
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eftsoons (adv.)
obsolete or archaic way of saying "soon afterward," from Old English eftsona "a second time, repeatedly, soon after, again," from eft "afterward, again, a second time" (from Proto-Germanic *aftiz, from PIE root *apo- "off, away") + sona "immediately" (see soon). With adverbial genitive. Not in living use since 17c.
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just (adv.)

c. 1400, "precisely, exactly;" late 15c., "fittingly, snugly;" c. 1500, "immediately;" from just (adj.) and paralleling the adverbial use of French juste (also compare Dutch juist, German just, from the adjectives).

The original sense of "exactly" in space, time, kind, or degree; "precisely, without interval, deviation, or variation" is preserved in just so"exactly that, in that very way" (1751), just as I thought, etc. But the sense decayed, as it often does in general words for exactness (compare anon, soon), from "exactly, precisely, punctually" to "within a little; with very little but a sufficient difference; nearly; almost exactly;" then by 1660s to "merely, barely, by or within a narrow margin (as in just missed). Hence just now as "a short time ago" (1680s). Also "very lately, within a brief period of time" (18c.). It is also used intensively, "quite" (by 1855).

Just-so story is attested 1902 in Kipling, from just so "exactly that, in that very way."

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hasta luego 
Spanish, "until soon;" salutation in parting.
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sub-deb (n.)
"girl who will soon 'come out;'" hence, "girl in her mid-teens," 1917, from sub- + deb.
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a.s.a.p. 

also asap, adverbial phrase pronounced either as a word (acronym) or as four letters (initialism), 1920, in a list of abbreviations recommended for secretaries in dental offices, from initial letters of phrase as soon as possible. The article (Walter E. Fancher, D.D.S., "The Practical Application of the Dental Hygienist in General Practice," in Oral Hygiene, March 1920) also has A.S.A.C. for as soon as convenient.

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knee-jerk (n.)
patellar reflex, a neurological phenomenon discovered and named in 1876; see knee (n.) + jerk (n.1) in the medical sense. The figurative use appeared soon after the phrase was coined.
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timely (adv.)
late Old English timlic "quickly, soon;" see time (n.) + -ly (2). As an adjective meaning "occurring at a suitable time" it is attested from c. 1200.
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pronto (adv.)

"promptly, soon, quickly," 1850, from Spanish pronto "ready, prompt," from Latin promptus (see prompt (v.)). The Italian cognate of the Spanish word, pronto, had been used in English by 1740 in musical instructions.

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weenie (n.)
"frankfurter," 1906, with slang sense of "penis" following soon after, from German wienerwurst "Vienna sausage" (see wiener). Meaning "ineffectual person, effeminate young man" is slang from 1963; pejorative sense via penis shape, or perhaps from weenie in the sense of "small" (see wee).
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