"ungrateful person," 1670s, from earlier adjective meaning "unfriendly," also "ungrateful, unthankful" (14c.), from Latin ingratus "unpleasant, disagreeable," also "ungrateful, unthankful," and "thankless, unprofitable," from in- "not" (see in- (1)) + gratus "pleasing, beloved, dear, agreeable" (from suffixed form of PIE root *gwere- (2) "to favor").
1640s, from Late Latin inimicalis "hostile," from Latin inimicus "unfriendly; an enemy" (see enemy).
Inimical expresses both feeling and action, generally in private affairs. Hostile also expresses both feeling and action, but applies especially to public affairs: where it applies to private matters, it expresses either strong or conspicuous action or feeling, or both, or all. [Century Dictionary, 1889]
early 13c., descorde, "unfriendly feeling, ill will;" also "dissension, strife," from Old French descorde (12c.) "disagreement," from Latin discordia, from discors (genitive discordis) "disagreeing, disagreement," from dis- "apart" (see dis-) + cor (genitive cordis) "heart," from PIE root *kerd- "heart."
Musical sense "want of harmony between two notes sounded together; a combination of notes not in harmony with one another" is from late 14c.
Northern English and Scottish survival of Middle English fremed "foreign; remote; unfamiliar; not related; unheard-of; unfriendly, distant and formal;" as a noun, "a stranger," from Old English fremde (Northumbrian fremþe); cognate with Old Saxon fremithi, Old Frisian fremed, Dutch vreemd, Old High German framidi, German fremd, Gothic framaþs "strange, foreign." In the Old English glossaries, fremde glosses Latin exter, alienus.
late 14c., "contrary, opposing," from Old French advers, earlier avers (13c., Modern French adverse) "antagonistic, unfriendly, contrary, foreign" (as in gent avers "infidel race"), from Latin adversus "turned against, turned toward, fronting, facing," figuratively "hostile, adverse, unfavorable," past participle of advertere "to turn toward," from ad "to" (see ad-) + vertere "to turn, turn back; be turned; convert, transform, translate; be changed" (from PIE root *wer- (2) "to turn, bend"). For distinction of use, see averse. Related: Adversely.
Old English uncuð "unknown, strange, unusual; uncertain, unfamiliar; unfriendly, unkind, rough," from un- (1) "not" + cuð "known, well-known," past participle of cunnan "to know" (see can (v.1)), from PIE root *gno- "to know." Meaning "strange, crude, clumsy" is first recorded 1510s. The compound (and the thing it describes) widespread in IE languages, such as Latin ignorantem, Old Norse ukuðr, Gothic unkunþs, Sanskrit ajnatah, Armenian ancanaut', Greek agnotos, Old Irish ingnad "unknown."
"unfriendly opponent, enemy" (originally especially of Satan as the enemy of mankind), mid-14c., aduersere, from Anglo-French adverser (13c.), Old French adversarie (12c., Modern French adversaire) "hostile opponent, enemy," or directly from Latin adversarius "an opponent, rival, enemy," noun use of adjective meaning "opposite, hostile, contrary," literally "turned toward one," from adversus "turned against, turned toward, fronting, facing," figuratively "hostile, adverse, unfavorable," past participle of advertere "to turn toward," from ad "to" (see ad-) + vertere "to turn, turn back, be turned; convert, transform, translate; be changed" (see versus). The Latin word is glossed in Old English by wiðerbroca.
early 13c., "one hateful toward and intent on harming (someone)," from Old French enemi (12c., Modern French ennemi), earlier inimi (9c.) "enemy, adversary, foe; demon, the Devil," from Latin inimicus "an enemy," literally "an unfriend," noun use of adjective meaning "hostile, unfriendly" (source also of Italian nemico, Catalan enamic, Spanish enemigo, Portuguese inimigo), from in- "not" (see in- (1)) + amicus "friend" related to amare "to love" (see Amy). From c. 1300 in English as "adversary of God, unbeliever, heathen, anti-Christian;" late 14c. as "the Devil;" also late 14c. as "member of an armed, hostile body in a war, feud, etc.;" of the opposing military forces as a whole, from c. 1600. From mid-14c. as an adjective.
Most Indo-European words for "personal enemy" cover also "enemy in war," but certain languages have special terms for the latter, such as Greek polemioi (distinct from ekhthroi), Latin hostis, originally "stranger" (distinct from inimicus), Russian neprijatel' (distinct from vrag). Russian vrag (Old Church Slavonic vragu) is cognate with Lithuanian vargas "misery" (see urge (v.)), and probably is related to Proto-Germanic *wargoz, source of Old Norse vargr "outlaw," hence "wolf;" Icelandic vargur "fox;" Old English wearg "criminal, felon;" which likely were the inspirations for J.R.R. Tolkien's warg as the name of a kind of large ferocious wolf in "The Hobbit" (1937) and "Lord of the Rings." Related: Enemies.