Etymology
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intrusion (n.)
late 14c., "unjust invasion of property or usurpation of office," from Old French intrusion (14c.), from Medieval Latin intrusionem (nominative intrusio) "a thrusting in," noun of action from past participle stem of Latin intrudere "to thrust in, force in," from in- "in" (from PIE root *en "in") + trudere "to thrust, push," from PIE *treud- "to press, push, squeeze" (see threat).

Meaning "a thrusting or pushing in" is from 1590s; that of "act of intruding" is from 1630s. Geological sense is from 1816.
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intrusive (adj.)
c. 1400, "usurping," from Latin intrus-, past participle stem of intrudere (see intrusion) + -ive. Meaning "coming unbidden" is from 1640s. Geological sense "thrust in out of regular place" is from 1826. Related: Intrusively; intrusiveness.
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intrude (v.)
early 15c., in an ecclesiastical sense, "take possession of (a prebend) not rightfully one's own," a back-formation from intrusion, or else from Latin intrudere "to thrust in, force in," from in- "in" (from PIE root *en "in") + trudere "to thrust, push," from PIE *treud- "to press, push, squeeze" (see threat).

From 1560s in a physical sense of "thrust in" (transitive or intransitive); meaning "enter unbidden and without welcome" is from 1570s; that of "thrust or bring in without necessity or right" is from 1580s. Related: Intruded; intruding.
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armlet (n.)
1530s, "metal band or ring worn around the upper arm," diminutive of arm (n.1) with -let. Compare bracelet. The Latin word was armilla. As "a small intrusion of the sea into the land," also 1530s.
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privacy (n.)

1590s, "a private or personal matter, a secret;" c. 1600 as "seclusion, state of being in retirement from company or the knowledge and observation of others," from private (adj.) + abstract noun suffix -cy. Meaning "state of freedom from intrusion or interference" is from 1814. Earlier was privatie (late 14c. as "secret, mystery;" c. 1400 as "a secret, secret deed; solitude, privacy"), from Old French privauté.

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astound (v.)
mid-15c., from Middle English astouned, astoned (c. 1300), past participle of astonen, astonien "to stun" (see astonish), with more of the original sense of Vulgar Latin *extonare. The unusual form is perhaps because the past participle was so much more common it came to be taken for the infinitive, or/and by the same pattern which produced round (v.) from round (adj.), or by the intrusion of an unetymological -d as in sound (n.1). Related: Astounded; astounding.
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advantage (n.)

early 14c., avantage, "position of being in advance of another," from Old French avantage "advantage, profit; superiority" (12c.), from avant "before," probably via an unrecorded Late or Medieval Latin *abantaticum, from Latin abante "from before," composed of ab "from" (see ab-) + ante "before, in front of, against" (from PIE root *ant- "front, forehead"). Compare advance (v.).

Advantage is the possession of a good vantage-ground for the attainment of ulterior objects of desire .... [Century Dictionary]

The unetymological -d- is a 16c. intrusion on the analogy of Latin ad- words. Meaning "any condition favorable to success, a favoring circumstance" (the opposite of a disadvantage) is from late 15c. Tennis score sense is from 1640s (in the writings of John Milton). Phrase to take advantage of is from late 14c. as "avail oneself of," also "impose upon." To have the advantage of (someone) "have superiority over" is from 1560s.

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crumble (v.)

late 15c., kremelen, "to break into small fragments" (transitive), from Old English *crymelan, presumed frequentative of gecrymman "to break into crumbs," from cruma (see crumb). Intransitive sense of "fall into small pieces" is from 1570s.

The -b- is from 16c., probably on analogy of crumb (where it also is an unetymological intrusion) or of French-derived words like humble, where it belongs. Related: Crumbled; crumbling. Old English gecrymman yielded Middle English crimen "to crumble" (transitive).

As a noun, from 1570s as "a fragment," from 1947 in cookery as dessert dish with a crumb topping, British English. "The technique itself seems to have been a product of Second World War culinary making-do" [Ayto, "Diner's Dictionary"].

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invasion (n.)
Origin and meaning of invasion

mid-15c., invasioun, "an assault, attack, act of entering a country or territory as an enemy," from Old French invasion "invasion, attack, assault" (12c.), from Late Latin invasionem (nominative invasio) "an attack, invasion," noun of action from past-participle stem of Latin invadere "to go, come, or get into; enter violently, penetrate into as an enemy, assail, assault, make an attack on," from in- "in" (from PIE root *en "in") + vadere "to go, to walk, go hastily," from PIE root *wadh- (2) "to go" (source also of Old English wadan "to go," Latin vadum "ford;" see wade (v.)).

In extended sense, of diseases, "a harmful incursion of any kind;" with reference to rights, etc., "infringement by intrusion, encroachment by entering into or taking away what belongs to another."

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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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