Online Etymology Dictionary

unwelcome (adj.): early 14c., from un- (1) "not" + welcome (adj.). Similar formation in Middle Dutch onwillecome, German unwillkommen.
upwind (adv.): also up-wind, 1838, from up (adv.) + wind (n.1). Originally a nautical term. As an adjective from 1892.
waterfowl (n.): early 14c., from water (n.1) + fowl (n.). Similar formation in Old High German wazzarvogel, Dutch watervogel.
waterspout (n.): late 14c., "drainpipe," from water (n.1) + spout (n.). Meaning "whirlwind on open water" is recorded from 1738.
windsurf (v.): also wind-surf, 1969, from wind (n.1) + surf (v.). Related: Windsurfed; windsurfing.
unpaid (adj.): late 14c., in reference to persons, from un- (1) "not" + past participle of pay (v.). Of debts, attested from late 15c.
unparalleled (adj.): 1590s, from un- (1) "not" + past participle of parallel (v.). Unparallel as an adjective is recorded from 1650s.
unpopular (adj.): 1640s, from un- (1) "not" + popular (adj.). Related: Unpopularly. Less common impopular is attested from 1721.
unresolved (adj.): 1570s, "undecided" (of questions), from un- (1) "not" + past participle of resolve (v.). Meaning "uncertain in opinion" is attested from 1590s.
unrequited (adj.): 1540s, from un- (1) "not" + past participle of requite (v.). The earliest reference is to love.
unreconstructed (adj.): 1867, "not reconciled to the outcome of the American Civil War," from un- (1) "not" + past participle of reconstruct (v.). See Reconstruction.
unpublished (adj.): c. 1600, from un- (1) "not" + past participle of publish. In reference to an author, attested from 1934.
unprincipled (adj.): 1630s, "not instructed" (in something), from un- (1) "not" + principled (adj.). Meaning "not honorable" is recorded from 1640s.
unschooled (adj.): 1580s, "untrained," from un- (1) "not" + past participle of school (v.). A verb unschool is attested from 1820.
unselfish (adj.): 1690s, from un- (1) "not" + selfish (adj.). Similar formation in Danish uselvisk, Swedish osjälfvisk. Related: Unselfishly; unselfishness.
unshaken (adj.): mid-15c., "not agitated," from un- (1) "not" + shaken. Meaning "not moved from a firm position" is recorded from 1540s.
unsuccessful (adj.): 1610s, from un- (1) "not" + successful (adj.). Related: Unsuccessfully. A noun unsuccess "lack of success" is recorded from 1580s.
unsure (adj.): c. 1400, "not safe against attack," also "lacking certainty," from un- (1) "not" + sure (adj.).
unsociable (adj.): c. 1600, from un- (1) "not" + sociable (adj.). Insociable is older (1580s) but less common.
unsophisticated (adj.): 1620s, "unmixed," from un- (1) "not" + sophisticated (adj.). Meaning "ingenuous, natural, inexperienced" is recorded from 1660s.
unyielding (adj.): 1590s of persons; 1650s, of substances; from un- (1) "not" + yielding (see yield (v.)).
unwonted (adj.): "not usual," 1550s, from un- (1) "not" + wonted. Earlier (and more correctly) unwont (c. 1400).
untenable (adj.): 1640s, "indefensible, incapable of being held against attack," from un- (1) "not" + tenable (adj.). Figurative sense is recorded from 1690s.
unused (adj.): c. 1300, "unaccustomed," from un- (1) "not" + past participle of use (v.). Meaning "not employed" is recorded from late 14c.
unimpaired (adj.): 1580s, from un- (1) "not" + past participle of impair (v.). Rare before c. 1760.
unimportant (adj.): 1750, from un- (1) "not" + important (adj.). Used earlier in a sense of "unassuming, modest" (1727). Related: Unimportantly.
uninterrupted (adj.): c. 1600, "continuous;" 1650s, "undisturbed," from un- (1) "not" + past participle of interrupt. Related: Uninterruptedly.
uninvited (adj.): "not having been invited," 1630s, from un- (1) "not" + past participle of invite (v.).
unjust (adj.): late 14c., of persons, "sinful; perpetrating injustice," from un- (1) "not" + just (adj.). Of actions, from c. 1400. Related: Unjustly.
unbeseeming (adj.): 1580s, "not befitting, inappropriate, unsuitable," from un- (1) "not" + beseeming. A common 17c. word.
undecided (adj.): 1530s, "not decided, unsettled," from un- (1) "not" + past participle of decide (v.).
undistinguished (adj.): 1590s, "not kept distinct," from un- (1) "not" + distinguished. Meaning "not elevated above others" is attested from c. 1600.
undoubted (adj.): mid-15c., from un- (1) "not" + past participle of doubt (v.). Related: Undoubtedly.
unicameral (adj.): 1853, from uni- "one" + Late Latin camera "chamber" (see camera) + -al (1).
unmade (adj.): mid-13c., "not yet made, unfinished, incomplete," from un- (1) "not" + past participle of make (v.).
unlovely (adj.): late 14c., "not evoking feelings of love," from un- (1) "not" + lovely. Meaning "ugly" is recorded from 1390s.
unlooked (adj.): c. 1300, "neglected," from un- (1) "not" + past participle of look (v.). With for, "unexpected," attested from 1530s.
unbuckle (v.): late 14c., from un- (2) "reverse of" + buckle (v.1). Related: Unbuckled; unbuckling.
undemonstrative (adj.): 1826, "not characterized by outward expression of feelings," from un- (1) "not" + demonstrative (adj.).
undeniable (adj.): 1540s, from un- (1) "not" + deny + -able. In 19c., often with a sense of "undeniably good." Related: Undeniably.
unerring (adj.): 1640s (implied in unerringly), from un- (1) "not" + verbal noun from err. Related: Unerringly.
unfeigned (adj.): late 14c., "sincere, genuine, true, real," from un- (1) "not" + past participle of feign (v.).
unflinching (adj.): 1728, from un- (1) "not" + present participle adjective of flinch (v.). Related: Unflinchingly.
unassuming (adj.): "unpretentious, modest," 1726, from un- (1) "not" + present participle of assume (v.). Related: Unassumingly.
unapproachable (adj.): 1580s, of places, from un- (1) "not" + approachable. Of persons, "distant, aloof," attested from 1848. Related: Unapproachably.
unabridged (adj.): 1590s, from un- (1) "not" + past participle of abridge (v.). Since 19c. chiefly in reference to literary works.
unconvinced (adj.): 1670s, from un- (1) "not" + past participle of convince (v.). Unconvincing is recorded from 1650s.
uncritical (adj.): 1650s, from un- (1) "not" + critical. Similar formation in Dutch onkritisch, German unkritisch, Danish unkritisk. Related: Uncritically.
undigested (adj.): 1520s, from un- (1) "not" + past participle of digest (v.). Figurative sense is recorded from c. 1600.
undisguised (adj.): c. 1500, in reference to things, from un- (1) "not" + past participle of disguise (v.). Of persons, attested from 1670s.