Etymology
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betray (v.)
early 13c., "prove false, violate by unfaithfulness;" c. 1300, bitrayen, "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").

From 1580s as "unintentionally show a true character;" 1690s as "indicate what is not obvious." From 1735 as "reveal or disclose in violation of confidence." Sometimes in Middle English also bitraish, betrash, from the French present participle stem. Related: Betrayed; betraying.
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careen (v.)

1590s, "to turn a ship on its side" (with the keel exposed, for inspection, repairs, etc.), from French cariner, literally "to expose a ship's keel," from French carene "keel" (16c.), from Italian (Genoese dialect) carena, from Latin carina "keel of a ship," also (and perhaps originally) "nutshell," possibly from PIE root *kar- "hard."

Intransitive sense of "to lean, to tilt" is from 1763 of ships; in general use by 1883. In sense "to rush headlong," confused with career (v.) at least since 1923. [To career is to move rapidly; to careen is to lurch from side to side, often while moving rapidly.] Earlier figurative uses of careen were "to be laid up; to rest." Related: Careened; careening.

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ostensible (adj.)

1730, "capable of being shown, that can be shown or seen, presentable," from French ostensible, from Latin ostens-, past-participle stem of ostendere "to show, expose to view; to stretch out, spread before; exhibit, display," from assimilated form of ob "in front of" (see ob-) + tendere "to stretch," from PIE root *ten- "to stretch." Meaning "apparent, professed, put forth or held out as real" is from 1771.

Ostensible is, literally, that may be or is held out as true, real, actual, or intended, but may or may not be so: thus, a person's ostensible motive for some action is the motive that appears to the observer, and is held out to him as the real motive, which it may or may not be. [Century Dictionary, 1895]
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*bhreu- 
also *bhreuə-, *bhreəu-, Proto-Indo-European root meaning "to boil, bubble, effervesce, burn," with derivatives referring to cooking and brewing.

It forms all or part of: barm; barmy; bourn (n.1) "small stream;" braise; bratwurst; brawn; brawny; braze (v.1) "to expose to the action of fire;" brazier; Brazil; bread; breed; brew; broth; broil (v.2) "to quarrel, brawl;" brood; effervesce; effervescence; effervescent; embroil; ferment; fervent; fervid; fervor; imbroglio.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit bhurnih "violent, passionate;" Greek phrear "well, spring, cistern;" Latin fervere "to boil, foam," Thracian Greek brytos "fermented liquor made from barley;" Russian bruja "current;" Old Irish bruth "heat;" Old English breowan "to brew," beorma "yeast;" Old High German brato "roast meat."
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offer (v.)

Middle English offeren, from Old English ofrian "to bring or put forward, to make a presentation, to show, exhibit;" also "to sacrifice, present something solemnly or worshipfully as a religious sacrifice, bring an oblation," from Latin offerre "to present, bestow, bring before" (in Late Latin "to present in worship"), from assimilated form of ob "to" (see ob-) + ferre "to bring, to carry," from PIE root *bher- (1) "to carry," also "to bear children."

From early 15c. as "to present (something) for acceptance or rejection." From 1530s as "to attempt to do." Commercial sense of "to expose for sale" is from 1630s. The Latin word was borrowed widely in Germanic languages in the religious sense via Christianity: Old Frisian offria, Middle Dutch offeren, Old Norse offra. The non-religious senses in English were from or reinforced by sense of Old French offrir "to offer," which is from Latin offerre. Related: Offered; offering.

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fire (v.)

c. 1200, furen, "arouse, inflame, excite" (a figurative use); literal sense of "set fire to" is attested from late 14c., from fire (n.). The Old English verb fyrian "to supply with fire" apparently did not survive into Middle English. Related: Fired; firing.

Meaning "expose to the effects of heat or fire" (of bricks, pottery, etc.) is from 1660s. Meaning "to discharge artillery or a firearm" (originally by application of fire) is from 1520s; extended sense of "to throw (as a missile)" is from 1580s. Fire away in the figurative sense of "go ahead" is from 1775.

The sense of "sack, dismiss from employment" is recorded by 1877 (with out; 1879 alone) in American English. This probably is a play on the two meanings of discharge (v.): "to dismiss from a position," and "to fire a gun," influenced by the earlier general sense "throw (someone) out" of some place (1871). To fire out "drive out by or as if by fire" (1520s) is in Shakespeare and Chapman. Fired up "angry" is from 1824 (to fire up "become angry" is from 1798).

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pledge (n.)

mid-14c., plegge, "surety, bail," from Old French plege (Modern French pleige) "hostage, security, bail," also Anglo-Latin plegium, both probably from Frankish *plegan "to guarantee," from *pleg-, a West Germanic root meaning "have responsibility for" (source also of Old Saxon plegan "vouch for," Middle Dutch plien "to answer for, guarantee," Old High German pflegan "to care for, be accustomed to," Old English pleon "to risk the loss of, expose to danger"), from PIE root *dlegh- "to engage oneself, be or become fixed" [Watkins].

From late 14c. as "person who goes surety or gives bail for another;" late 15c. (Caxton) as "personal property given as surety for a debt or engagement. By 1520s as "a token or sign of favor, agreement, etc.

Meaning "allegiance vow attested by drinking with another" is from 1630s. Sense of "solemn promise, one's word given or considered as security for the performance (or refraining from) an act" is recorded by 1814, though this notion is from 16c. in the verb. Weekley notes the "curious contradiction" in pledge (v.) "to toast with a drink" (1540s) and pledge (n.) "the vow to abstain from drinking" (1833). Meaning "student who has agreed to join a fraternity or sorority" dates from 1901.

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burn (v.)

early 12c., brennen, "be on fire, be consumed by fire; be inflamed with passion or desire, be ardent; destroy (something) with fire, expose to the action of fire, roast, broil, toast; burn (something) in cooking," of objects, "to shine, glitter, sparkle, glow like fire;" chiefly from Old Norse brenna "to burn, light," and also from two originally distinct Old English verbs: bærnan "to kindle" (transitive) and beornan "be on fire" (intransitive).

All these are from Proto-Germanic *brennanan (causative *brannjanan),source also of Middle Dutch bernen, Dutch branden, Old High German brinnan, German brennen, Gothic -brannjan "to set on fire;" but the ultimate etymology is uncertain. Related: Burned/burnt (see -ed); burning.

Figurative use (of passions, battle, etc.) was in Old English. Meaning "be hot, radiate heat" is from late 13c. Meaning "produce a burning sensation, sting" is from late 14c. Meaning "cheat, swindle, victimize" is first attested 1650s. In late 18c, slang, burned meant "infected with venereal disease."

To burn one's bridges(behind one) "behave so as to destroy any chance of returning to a status quo" (attested by 1892 in Mark Twain), perhaps ultimately is from reckless cavalry raids in the American Civil War. Of money, to burn a hole in (one's) pocket "affect a person with a desire to spend" from 1850.

Slavic languages have historically used different and unrelated words for the transitive and intransitive senses of "set fire to"/"be on fire:" for example Polish palić/gorzeć, Russian žeč'/gorel.

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debunk (v.)

"expose false or nonsensical claims or sentiments," 1923, from de- + bunk (n.2); apparently first used by U.S. novelist William Woodward (1874-1950), in his best-seller "Bunk;" the notion being "to take the bunk out of things." It got a boost from Harold U. Faulkner's "Colonial History Debunked" [Harper's Magazine, December 1925], which article itself quickly was debunked, and the word was in vogue in America in the mid-1920s. Related: Debunked; debunking.

Wets and Drys, Fundamentalists and Modernists, are busily engaged in debunking one another to the delight and edification of a public which divides its time between automobiling and listening-in. Is it art, or education, or religion that you prefer? You have only to get the right station and what you last heard about the matter will be cleverly debunked while you wait. [Carl Vernon Tower, "Genealogy 'Debunked," in Annual Reports of the Tower Genealogical Society, 1925]

It was, naturally, execrated in England.

The origin of to debunk is doubtless the same as that of American jargon in general — the inability of an ill-educated and unintelligent democracy to assimilate long words. Its intrusion in our own tongue is due partly to the odious novelty of the word itself, and partly to the prevailing fear that to write exact English nowadays is to be put down as a pedant and a prig. [letter to the editor, London Daily Telegraph, March 2, 1935, cited in Mencken, "The American Language"]
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discover (v.)

c. 1300, discoveren, "divulge, reveal, disclose, expose, lay open to view, betray (someone's secrets)," senses now obsolete, from stem of Old French descovrir "uncover, unroof, unveil, reveal, betray," from Medieval Latin discooperire, from Latin dis- "opposite of" (see dis-) + cooperire "to cover up, cover over, overwhelm, bury" (see cover (v.)).

At first with a sense of betrayal or malicious exposure (discoverer originally meant "informant"). Also in Middle English used in lteral senses, such as "to remove" (one's hat, the roof from a building). The meaning "to obtain the first knowledge or sight of what was before not known," the main modern sense, is by 1550s.

Discover, Invent, agree in signifying to find out; but we discover what already exists, though to us unknown; we invent what did not before exist: as, to discover the applicability of steam to the purposes of locomotion, and to invent the machinery necessary to use steam for these ends. ... Some things are of so mixed a character that either word may be applied to them. [Century Dictionary]

Sense of "make famous or fashionable" is by 1908. Related: Discovered; discovering.

That man is not the discoverer of any art who first says the thing; but he who says it so long, and so loud, and so clearly, that he compels mankind to hear him—the man who is so deeply impressed with the importance of the discovery that he will take no denial, but at the risk of fortune and fame, pushes through all opposition, and is determined that what he thinks he has discovered shall not perish for want of a fair trial. [Sydney Smith, in Edinburgh Review, June 1826]
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