Etymology
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contradict (v.)
Origin and meaning of contradict

1570s, "speak against, oppose" (a sense now obsolete); 1580s, "assert the contrary or opposite of," from Latin contradictus, past participle of contradicere, in classical Latin contra dicere "to speak against," from contra "against" (see contra (prep., adv.)) + dicere "to say, speak" (from PIE root *deik- "to show," also "pronounce solemnly").

Meaning "deny the words or assertions of, speak in contradiction" is from c. 1600. Of statements, etc., "be inconsistent with," c. 1600. Related: Contradicted; contradicting; contradictive.

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obloquy (n.)

mid-15c., obloquie, "evil speaking, slander, calumny, derogatory remarks," from Medieval Latin obloquium "speaking against, contradiction," from Latin obloqui "to speak against, contradict," from ob "against" (see ob-) + loqui "to speak," from PIE root *tolkw- "to speak." Related: Obloquious.

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disprove (v.)

"prove to be false or erroneous," late 14c., from Old French desprover "refute, contradict," from des- (see dis-) + prover "show; convince; put to the test" (see prove). Related: Disproved; disproving; disprovable. Middle English also had dispreven, from Old French desprover, with substitution of prefix.

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recant (v.)

"to unsay, to contradict or withdraw a declaration or proposition," 1530s, from Latin recantare "recall, revoke," from re- "back" (see re-) + cantare, literally "to chant, to sing" (from PIE root *kan- "to sing"). The English word is from the Reformation; the Latin verb is a loan-translation of Greek palinoidein "recant," from palin "back" + oeidein "to sing." Related: Recanted; recanting. It was used occasionally 17c. in an etymological sense of "sing over again" (with re- = "again").

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belie (v.)
Old English beleogan "to deceive by lies," from be- + lie (v.1) "to lie, tell lies." Current sense of "to contradict as a lie, give the lie to, show to be false" is first recorded 1640s.

The other verb lie once also had an identical variant form, from Old English belicgan, which meant "to encompass, beleaguer," and in Middle English was a euphemism for "to have sex with" (i.e. "to lie with carnally").
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gainsay (v.)
"contradict, deny, dispute," c. 1300, literally "say against," from gain- (Old English gegn- "against;" see again) + say (v.). In Middle English it translates Latin contradicere. "Solitary survival of a once common prefix" [Weekley]. It also figured in such now-obsolete compounds as gain-taking "taking back again," gainclap "a counterstroke," gainbuy "redeem," Gaincoming "Second Advent," and gainstand "to oppose." Related: Gainsaid; gainsaying.
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oppose (v.)

late 14c., opposen, "to speak or act against; accuse, question, interrogate," from Old French oposer "oppose, resist, rival; contradict, state opposing point of view" (12c.), apparently from assimilated form of Latin ob- "in the direction of, in front of" (see ob-) + French poser "to place, lay down" (see pose (v.1)), with the sense blended with that of Latin opponere "oppose, object to, set against" (see opponent). The meaning "to set or place over against or directly opposite" (transitive) and "interpose effort or objection, be adverse, act adversely" (intransitive) are from 1590s. Related: Opposed; opposing.

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contradictory (adj.)

1530s, "mutually opposed, at variance, inconsistent, incapable of being true together," from Late Latin contradictorius "containing a contradiction or objection," from contradictus, past participle of contradicere "to speak against" (see contradiction).

Sense of "denying that something stated or approved is completely true" is from c. 1600. Meaning "fond of contradicting" is from 1891. Other adjectives, now obsolete, in the same sense were contradictorious (early 15c.), contradictious (c. 1600), contradictive (1620s). Related: Contradictorily. Used earlier as a noun (late 14c.) in plural contradictories, "a pair of propositions inconsistent with each other."

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contradiction (n.)

late 14c., "objection, opposition; hostility, mutual opposition," also "absolute inconsistency," from Old French contradiction or directly from Late Latin contradictionem (nominative contradictio) "a reply, objection, counterargument," noun of action from past-participle stem of contradicere, in classical Latin contra dicere "to speak against, oppose in speech or opinion," from contra "against" (see contra) + dicere "to say, speak" (from PIE root *deik- "to show," also "pronounce solemnly"). Old English used wicwedennis as a loan-translation of Latin contradictio.

Meaning "an assertion of the direct opposite of what has been said or affirmed" is from c. 1400. Sense of "a contradictory fact or condition" is from 1610s.  Contradiction in terms "self-contradictory phrase" is attested from 1705. 

[C]ontradictions become elegance and propriety of language, for a thing may be excessively moderate, vastly little, monstrous pretty, wondrous common, prodigious natural, or devilish godly .... [Abraham Tucker, "The Light of Nature Pursued," 1805]
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dissent (v.)

mid-15c., dissenten, "express a different or contrary opinion or feeling, withhold approval or consent," from Old French dissentir (15c.) and directly from Latin dissentire "differ in sentiments, disagree, be at odds, contradict, quarrel," from dis- "differently" (see dis-) + sentire "to feel, think" (see sense (n.)). Ecclesiastical sense of "refuse to be bound by the doctrines or rules of an established church" is from 1550s. Related: Dissented; dissenting.

The noun is 1580s, "difference of opinion with regard to religious doctrine or worship," from the verb. From 1650s as "the act of dissenting, refusal to be bound by what is contrary to one's own judgment" (the opposite of consent). From 1660s as "a declaration of disagreement." By 1772 in the specific sense of "refusal to conform to an established church." 

Has there ever been a society which has died of dissent? Several have died of conformity in our lifetime. [Jacob Bronowski "Science and Human Values," 1956]
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