untreatable (adj.) Look up untreatable at Dictionary.com
late 14c., "unmanageable," from un- (1) "not" + treatable (see treat (v.)). In medicine, of diseases, conditions, etc., by 1865.
untried (adj.) Look up untried at Dictionary.com
1510s, "not proven or tested," from un- (1) "not" + tried.
untrodden (adj.) Look up untrodden at Dictionary.com
c. 1300, from un- (1) "not" + past participle of tread (v.).
untroubled (adj.) Look up untroubled at Dictionary.com
late 15c., from un- (1) "not" + past participle of trouble (v.).
untrue (adj.) Look up untrue at Dictionary.com
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.) Look up untrustworthy at Dictionary.com
1846, from un- (1) "not" + trustworthy. Related: Untrustworthiness.
untruth (n.) Look up untruth at Dictionary.com
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.) Look up unturned at Dictionary.com
1540s, from un- (1) "not" + past participle of turn (v.).
untwist (v.) Look up untwist at Dictionary.com
1530s, from un- (2) "reverse, opposite of" + twist (v.). Related: Untwisted; untwisting.
unusable (adj.) Look up unusable at Dictionary.com
1825, from un- (1) "not" + usable (adj.).
unused (adj.) Look up unused at Dictionary.com
c. 1300, "unaccustomed," from un- (1) "not" + past participle of use (v.). Meaning "not employed" is recorded from late 14c.
unusual (adj.) Look up unusual at Dictionary.com
1580s, from un- (1) "not" + usual (adj.). Related: Unusually.
unutterable (adj.) Look up unutterable at Dictionary.com
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.) Look up unvanquished at Dictionary.com
late 14c., from un- (1) "not" + past participle of vanquish (v.).
unvarnished (adj.) Look up unvarnished at Dictionary.com
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.) Look up unvarying at Dictionary.com
1680s, from un- (1) "not" + present participle of vary (v.).
unveil (v.) Look up unveil at Dictionary.com
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.) Look up unwanted at Dictionary.com
1690s, from un- (1) "not" + past participle of want (v.).
unwarranted (adj.) Look up unwarranted at Dictionary.com
1570s, from un- (1) "not" + past participle of warrant (v.).
unwary (adj.) Look up unwary at Dictionary.com
by 1570s, possibly late 14c., from un- (1) "not" + wary (adj.). Old English had unwær "incautious," unwærlic. Related: Unwarily.
unwashed (adj.) Look up unwashed at Dictionary.com
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.) Look up unwavering at Dictionary.com
1560s, from un- (1) "not" + present participle of waver (v.).
unwearied (adj.) Look up unwearied at Dictionary.com
mid-13c., from Old English ungewerigod, from un- (1) "not" + past participle of weary (v.).
unwed (adj.) Look up unwed at Dictionary.com
1510s, from un- (1) "not" + past participle of wed (v.). Unwedded "unmarried; celibate" is from c. 1200.
unwelcome (adj.) Look up unwelcome at Dictionary.com
early 14c., from un- (1) "not" + welcome (adj.). Similar formation in Middle Dutch onwillecome, German unwillkommen.
unwell (adj.) Look up unwell at Dictionary.com
mid-15c., "somewhat ill," from un- (1) "not" + well (adj.). Similar formation in North Frisian unwel, German unwohl.
unwholesome (adj.) Look up unwholesome at Dictionary.com
c. 1200, from un- (1) "not" + wholesome (adj.). Similar formation in Flemish onheylsaem, German unheilsam, Old Norse uheilsamr.
unwieldy (adj.) Look up unwieldy at Dictionary.com
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.) Look up unwilling at Dictionary.com
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.) Look up unwind at Dictionary.com
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.) Look up unwise at Dictionary.com
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.) Look up unwisely at Dictionary.com
Old English unwislice "foolishly;" see unwise + -ly (2).
unwitting (adj.) Look up unwitting at Dictionary.com
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.) Look up unwonted at Dictionary.com
"not usual," 1550s, from un- (1) "not" + wonted. Earlier (and more correctly) unwont (c. 1400).
unworkable (adj.) Look up unworkable at Dictionary.com
1784, from un- (1) "not" + workable (adj.).
unworldly (adj.) Look up unworldly at Dictionary.com
1707, from un- (1) "not" + worldly (adj.). Related: Unworldliness.
unworthy (adj.) Look up unworthy at Dictionary.com
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.) Look up unwound at Dictionary.com
"no longer wound," 1707, from un- (1) "not" + past participle of wind (v.1).
unwrap (v.) Look up unwrap at Dictionary.com
late 14c., from un- (2) "opposite of" + wrap (v.). Related: Unwrapped; unwrapping.
unwritten (adj.) Look up unwritten at Dictionary.com
mid-14c., from un- (1) "not" + past participle of write (v.). Similar formation in Old English unwriten, Old Norse uritinn.
unyielding (adj.) Look up unyielding at Dictionary.com
1590s of persons; 1650s, of substances; from un- (1) "not" + yielding (see yield (v.)).
unzip (v.) Look up unzip at Dictionary.com
1939, from un- (2) "opposite of" + zip (v.). Related: Unzipped; unzipping.
up (v.) Look up up at Dictionary.com
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.) Look up up at Dictionary.com
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.) Look up up at Dictionary.com
"that which is up," 1530s, from up (adv.). Phrase on the up-(and-up) "honest, straightforward" first attested 1863, American English.
up (adv.) Look up up at Dictionary.com
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 "under," also "up from under," hence also "over."

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- Look up up- at Dictionary.com
prefix with various senses, from Old English up (adv.), corresponding to similar prefixes in other Germanic languages.
up-and-down (adj.) Look up up-and-down at Dictionary.com
1610s, from adverbial phrase up and down (c. 1200); see up (adv.) + down (adv.).
up-country (n.) Look up up-country at Dictionary.com
"interior regions," 1680s, from up- + country (n.). As an adjective from 1810; as an adverb from 1864.
up-current (adj.) Look up up-current at Dictionary.com
1909, from up- + current (n.).