Etymology
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betray (v.)

early 13c., bitraien, "prove false, violate by unfaithfulness;" c. 1300, "deliver or expose to the power of an enemy by treachery," also "mislead, deceive, delude," from be- + obsolete Middle English tray, from Old French traine "betrayal, deception, deceit," from trair (Modern French trahir) "betray, deceive," from Latin tradere "hand over," from trans "across" (see trans-) + dare "to give" (from PIE root *do- "to give").

It is attested from 1580s as "unintentionally show a true character;" by 1690s as "indicate what is not obvious;" from 1735 as "reveal or disclose in violation of confidence." In Middle English it sometimes was also bitraish, betrash, from the French present-participle stem. Related: Betrayed; betraying.

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betrayer (n.)

"a traitor, seducer," 1520s, agent noun from betray (v.).

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betrayal (n.)

"act of betraying," 1798, from betray + -al (2). Earlier in the same sense were betrayment (1540s), betraying (late 14c.).

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*do- 

*dō-, Proto-Indo-European root meaning "to give."

It forms all or part of: add; anecdote; antidote; betray; condone; dacha; dado; data; date (n.1) "time;" dative; deodand; die (n.); donation; donative; donor; Dorian; Dorothy; dose; dowager; dower; dowry; edition; endow; Eudora; fedora; Isidore; mandate; Pandora; pardon; perdition; Polydorus; render; rent (n.1) "payment for use of property;" sacerdotal; samizdat; surrender; Theodore; Theodosia; tradition; traitor; treason; vend.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit dadati "gives," danam "offering, present;" Old Persian dadatuv "let him give;" Greek didomi, didonai, "to give, offer," dōron "gift;" Latin dare "to give, grant, offer," donum "gift;" Armenian tam "to give;" Old Church Slavonic dati "give," dani "tribute;" Lithuanian duoti "to give," duonis "gift;" Old Irish dan "gift, endowment, talent," Welsh dawn "gift."

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bewray (v.)

early 13c., biwreien, "to inform against;" mid-13c., "to speak ill of," from be- + Middle English wreien "betray," from Old English wregan "accuse" (cognate with Old Saxon wrogian, Dutch wroegen "accuse," Old High German ruogen, German rügen "to censure," Gothic wrohjan "accuse").

It has been perhaps somewhat influenced in sense by the unrelated betray. The sense of "reveal, expose" is from late 14c. "Probably more or less of a conscious archaism since the 17th c." [OED]. Related: Bewrayed; bewraying; bewrayment.

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two-time (v.)

"to deceive, cheat, betray," 1924, perhaps from notion of "to have two at a time." An earlier reference (1922) in a Kentucky criminal case involves a double-cross or betrayal without a romance angle. Related: two-timing (adj.); two-timer.

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job (v.)

1660s, "to buy and sell as a broker" (intransitive), from job (n.). Meaning "deal in public stocks on one's own account" is from 1721. Meaning "to cheat, betray" is from 1903; earlier "pervert public service to private advantage" (1732). Related: Jobbed; jobbing.

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peach (v.)

"to inform against, betray one's accomplices," 1560s (earlier pechen, "to accuse, indict, bring to trial," c. 1400), a shortening of appeach, empeach, obsolete variants of impeach. For form, compare peal (v.), also Middle English pelour "an accuser," from appellour. Related: Peached; peaching; peacher.

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manifest (v.)
Origin and meaning of manifest

late 14c., "to spread" (one's fame), "to show plainly," from manifest (adj.) or else from Latin manifestare "to discover, disclose, betray." Meaning "to display by actions" is from 1560s; reflexive sense, of diseases, etc., "to reveal as in operation" is from 1808. Related: Manifested; manifesting.

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give-away (n.)

also giveaway, "act of giving away," 1872, from verbal phrase give away, c. 1400 (of brides from 1719); see give (v.) + away (adv.). The phrase in the meaning "to betray, expose, reveal" is from 1878, originally U.S. slang. Hence also Related: give-away (n.) "inadvertent betrayal or revelation" (1882).

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