"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"]
"To be or remain in that posture in which the weight of the body rests upon the posteriors" [OED], Middle English sitten, from Old English sittan "occupy a seat, be seated, sit down, seat oneself; remain, continue; settle, encamp; lie in wait; besiege" (class V strong verb; past tense sæt, past participle seten), from Proto-Germanic *setjan (source also of Old Saxon sittian, Old Norse sitja, Danish sidde, Old Frisian sitta, Middle Dutch sitten, Dutch zitten, Old High German sizzan, German sitzen, Gothic sitan), from PIE root *sed- (1) "to sit."
With past tense sat (formerly also set, which is now restricted to dialect, and sate, now archaic); and past participle sat, formerly sitten. The meaning "to have a seat in a legislative assembly" is from late 14c.; in reference to the assembly, "to hold a session," from 1510s. The sense of "pose" for a portrait, etc., is by 1530s.
As short for babysit (v.) by 1966. The specific sense of "occupy a judicial seat" (Old English) is the notion in sit in judgement. The meaning "have a certain position or direction" is from c. 1200; of winds, "to blow from" (a certain quarter), 1590s, from the notion of "to be in."
To sit back "be inactive" is from 1943. To sit on one's hands originally was "withhold applause" (1926), later generalized to "do nothing" (by 1959). To sit around "be idle, do nothing" is by 1915, American English. To sit out "not take part, make oneself an exception" is from 1650s.
Middle English holden, earlier halden, from Old English haldan (Anglian), healdan (West Saxon), "to contain; to grasp; to retain (liquid, etc.); to observe, fulfill (a custom, etc.); to have as one's own; to have in mind (of opinions, etc.); to possess, control, rule; to detain, lock up; to foster, cherish, keep watch over; to continue in existence or action; to keep back from action," class VII strong verb (past tense heold, past participle healden), from Proto-Germanic *haldanan (source also of Old Saxon haldan, Old Frisian halda, Old Norse halda, Dutch houden, German halten "to hold," Gothic haldan "to tend").
Based on the Gothic sense (also present as a secondary sense in Old English), the verb is presumed originally in Germanic to have meant "to keep, tend, watch over" (as grazing cattle), later "to have." Ancestral sense is preserved in behold. The original past participle holden was replaced by held beginning 16c., but survives in some legal jargon and in beholden.
The modern use in the sense "lock up, keep in custody" is from 1903. Hold back in the figurative senses is from 1530s (transitive); 1570s (intransitive). To hold off is early 15c. (transitive), c. 1600 (intransitive). Hold on is early 13c. as "to maintain one's course," 1830 as "to keep one's grip on something," 1846 as an order to wait or stop.
To hold (one's) tongue "be silent" is from c. 1300. To hold (one's) own is from early 14c. To hold (someone's) hand in the figurative sense of "give moral support" is from 1935. To hold (one's) horses "be patient" is from 1842, American English; the notion is of keeping a tight grip on the reins. To have and to hold have been paired alliteratively at least since c. 1200, originally of marriage but also of real estate. To hold water in the figurative sense "be sound or consistent throughout" is from 1620s.
also gas-light, "light, or a provision for light, produced by combustion of coal gas; a gas-jet," 1808, from (illuminating) gas (n.1) + light (n.). Used through the 19th and into the early 20th century as street and domestic lighting. Related: Gas-lighted; gas-lighting; gaslighting.
As a verb meaning "to deliberately make a person believe that they are insane," by 1961, perhaps 1956. This sense is from the 1944 film Gaslight, in which a 19th century woman (played by Ingrid Bergman, who won an Academy Award) appears to be going mad. It is later revealed that her criminal husband has been convincing her that she is insane in order to discredit her observations of his activities. Among the observable clues has been the dimming of their home's gaslighting whenever (as she later learns) the husband goes secretly into the attic: he has convinced her that she is imagining this, until a family friend sees it, too, which confirms the clue that uncovers the crime.
Brian: Tell me. Is there anyone else in the house now, except us and Elizabeth?
Paula: No. Why?
Brian: The gas just went down.
Paula: You saw that too!
Brian: Why, yes.
Paula: Oh, then it really happens! I thought I imagined it!
Brian: But all it means is someone else has turned it on.
Paula: Oh, no, no. I thought that too. But every night, I’ve been all over the house, there’s never been another light turned on. At last I can tell this to someone! Every night when my husband goes out…
Brian: …The light goes down?
Brian: And then what?
Paula: Well, then, I think I hear things. I watch and wait. Later on, the gas goes up again.
Brian: And he comes back?
Paula: Yes. Quite soon after. Always quite soon after.
The word seems to have received a boost in feminist literature in late 1970s.
… I had been told that my tonsillectomy was “not that bad” or that the dentist whose hands were between my legs was “fixing my teeth,” … My own favorite embodiment of this horror, still enjoyed by late-show insomniacs, is the 1944 film Gaslight, a tale which so impressed the public imagination that even today the word “gaslight” is used to describe an attempt to destroy another’s perceptions of reality and, ultimately, sanity itself. [Florence Rush, "The Best Kept Secret: Sexual Abuse of Children," 1980]
The sense evolved by 2016 to also mean "dismiss or discredit someone's viewpoint."