Online Etymology Dictionary

untreatable (adj.): late 14c., "unmanageable," from un- (1) "not" + treatable (see treat (v.)). In medicine, of diseases, conditions, etc., by 1865.
untried (adj.): 1510s, "not proven or tested," from un- (1) "not" + tried.
untrodden (adj.): c. 1300, from un- (1) "not" + past participle of tread (v.).
untroubled (adj.): late 15c., from un- (1) "not" + past participle of trouble (v.).
untrue (adj.): Old English untreowe "unfaithful" (of persons), from un- (1) "not" + true (adj.). Similar formation in Middle Dutch ongetrouwe, Middle Low German ungetruwe, Old High German ungitriuwi, Old Norse utryggr. Meaning "contrary to facts" is attested from c. 1300.
untrustworthy (adj.): 1846, from un- (1) "not" + trustworthy. Related: Untrustworthiness.
untruth (n.): Old English untreowþ "unfaithfulness, treachery," from un- (1) "not" + truth (n.). Similar formation in Old Norse utrygð. Meaning "falsehood" is attested from mid-15c., as is that of "a lie." Related: Untruthful.
unturned (adj.): 1540s, from un- (1) "not" + past participle of turn (v.).
untwist (v.): 1530s, from un- (2) "reverse, opposite of" + twist (v.). Related: Untwisted; untwisting.
unusable (adj.): 1825, from un- (1) "not" + usable (adj.).
unused (adj.): c. 1300, "unaccustomed," from un- (1) "not" + past participle of use (v.). Meaning "not employed" is recorded from late 14c.
unusual (adj.): 1580s, from un- (1) "not" + usual (adj.). Related: Unusually.
unutterable (adj.): 1580s, from un- (1) "not" + utterable (see utter (v.)). As a noun, from 1788; unutterables as a euphemism for "trousers" is recorded by 1826 (see inexpressible).
unvanquished (adj.): late 14c., from un- (1) "not" + past participle of vanquish (v.).
unvarnished (adj.): c. 1600, of statements, "not embellished," from un- (1) "not" + past participle of varnish (v.). Literal sense of "not covered in varnish" is recorded from 1758.
unvarying (adj.): 1680s, from un- (1) "not" + present participle of vary (v.).
unveil (v.): 1590s, in reference to sight, "to make clear," from un- (2) "opposite of" + veil (v.). Sense of "to display or reveal" (something) is from 1650s. Related: Unveiled; unveiling.
unwanted (adj.): 1690s, from un- (1) "not" + past participle of want (v.).
unwarranted (adj.): 1570s, from un- (1) "not" + past participle of warrant (v.).
unwary (adj.): by 1570s, possibly late 14c., from un- (1) "not" + wary (adj.). Old English had unwær "incautious," unwærlic. Related: Unwarily.
unwashed (adj.): late 14c., from un- (1) "not" + past participle of wash (v.). Replaced Middle English unwashen, from Old English unwæscen. Noun sense of "the lower class" is attested from 1830.
unwavering (adj.): 1560s, from un- (1) "not" + present participle of waver (v.).
unwearied (adj.): mid-13c., from Old English ungewerigod, from un- (1) "not" + past participle of weary (v.).
unwed (adj.): 1510s, from un- (1) "not" + past participle of wed (v.). Unwedded "unmarried; celibate" is from c. 1200.
unwelcome (adj.): early 14c., from un- (1) "not" + welcome (adj.). Similar formation in Middle Dutch onwillecome, German unwillkommen.
unwell (adj.): mid-15c., "somewhat ill," from un- (1) "not" + well (adj.). Similar formation in North Frisian unwel, German unwohl.
unwholesome (adj.): c. 1200, from un- (1) "not" + wholesome (adj.). Similar formation in Flemish onheylsaem, German unheilsam, Old Norse uheilsamr.
unwieldy (adj.): late 14c., "lacking strength, powerless," from un- (1) "not" + obsolete wieldy, from Old English wielde "active, vigorous," from Proto-Germanic *walth- "have power" (see wield (v.)). Meaning "moving ungracefully" is recorded from 1520s; in reference to weapons, "difficult to handle, awkward by virtue of size or shape" it is attested from 1540s. Related: Unwieldiness.
unwilling (adj.): early 15c., altered from or re-formed to replace Middle English unwilland, from Old English unwillende; see un- (1) "not" + willing (adj.); see -ing (2). Related: Unwillingly; unwillingness.
unwind (v.): early 14c., "to undo" (a bandage, wrapping, etc.), from un- (2) "opposite of" + wind (v.1). Similar formation in Old English unwindan "unveil, uncover," Dutch ontwinden, Old High German intwindan. Reflexive sense is recorded from 1740; figurative sense of "to release oneself from tensions, to relax" is by 1938. Related: Unwound; unwinding.
unwise (adj.): Old English unwis, from un- (1) "not" + wise (adj.). Similar formation in Middle Dutch onwijs, Old High German unwis, German unweise, Old Norse uviss, Gothic unweis.
unwisely (adv.): Old English unwislice "foolishly;" see unwise + -ly (2).
unwitting (adj.): late 14c., altered from or re-formed to replace unwitand, from Old English unwitende "ignorant," from un- (1) "not" + witting (adj.); see -ing (2). Similar formation in Old High German unwizzanti, German unwissend, Old Norse uvitandi, Gothic unwitands. Rare after c. 1600; revived c. 1800. Related: Unwittingly.
unwonted (adj.): "not usual," 1550s, from un- (1) "not" + wonted. Earlier (and more correctly) unwont (c. 1400).
unworkable (adj.): 1784, from un- (1) "not" + workable (adj.).
unworldly (adj.): 1707, from un- (1) "not" + worldly (adj.). Related: Unworldliness.
unworthy (adj.): mid-13c., unwurði, from un- (1) "not" + worthy (adj.). Similar formation in Middle Dutch onwerdich, Dutch onwaardig, Middle Low German unwerdich, Old High German unwirdig, Old Norse uverðugr. Old English had unweorðlic. Related: Unworthiness.
unwound (adj.): "no longer wound," 1707, from un- (1) "not" + past participle of wind (v.1).
unwrap (v.): late 14c., from un- (2) "opposite of" + wrap (v.). Related: Unwrapped; unwrapping.
unwritten (adj.): mid-14c., from un- (1) "not" + past participle of write (v.). Similar formation in Old English unwriten, Old Norse uritinn.
unyielding (adj.): 1590s of persons; 1650s, of substances; from un- (1) "not" + yielding (see yield (v.)).
unzip (v.): 1939, from un- (2) "opposite of" + zip (v.). Related: Unzipped; unzipping.
up (adv.): Old English up, uppe, from Proto-Germanic *upp- "up" (source also of Old Frisian, Old Saxon up "up, upward," Old Norse upp; Danish, Dutch op; Old High German uf, German auf "up"; Gothic iup "up, upward," uf "on, upon, under;" Old High German oba, German ob "over, above, on, upon"), from PIE root *upo "up from below" (source also of Sanskrit upa "near, under, up to, on," Greek hypo "under, below," Latin sub "under;" see sub-).

As a preposition, "to a higher place" from c. 1500; also "along, through" (1510s), "toward" (1590s). Often used elliptically for go up, come up, rise up, etc. Up the river "in jail" first recorded 1891, originally in reference to Sing Sing, which is up the Hudson from New York City. To drive someone up the wall (1951) is from the notion of the behavior of lunatics or caged animals. Insulting retort up yours (scil. ass) attested by late 19c.
up (v.): 1550s, "to drive and catch (swans)," from up (adv.). Intransitive meaning "get up, rise to one's feet" (as in up and leave) is recorded from 1640s. Sense of "to move upward" is recorded from 1737. Meaning "increase" (as in up the price of oil) is attested from 1915. Compare Old English verb uppian "to rise up, swell." Related: Upped; upping. Upping block, used for mounting or dismounting horses, carriages, etc., is attested from 1796 (earlier was horsing-block, 1660s).
up (adj.): c. 1300, "dwelling inland or upland," from up (adv.). Meaning "going up" is from 1784. From 1815 as "excited, exhilarated, happy," hence "enthusiastic, optimistic." Up-and-coming "promising" is from 1848. Musical up-tempo (adj.) is recorded from 1948.
up (n.): "that which is up," 1530s, from up (adv.). Phrase on the up-(and-up) "honest, straightforward" first attested 1863, American English.
up-: prefix with various senses, from Old English up (adv.), corresponding to similar prefixes in other Germanic languages.
up-and-down (adj.): 1610s, from adverbial phrase up and down (c. 1200); see up (adv.) + down (adv.).
up-country (n.): "interior regions," 1680s, from up- + country (n.). As an adjective from 1810; as an adverb from 1864.
up-current (adj.): 1909, from up- + current (n.).