quack

Etymology 1

From Middle English *quacken, queken (“to croak like a frog; make a noise like a duck, goose, or quail”), from quack, qwacke, quek, queke (“quack”, interjection and noun), also kek, keke, whec-, partly of imitative origin and partly from Middle Dutch quacken (“to croak, quack”), from Old Dutch *kwaken (“to croak, quack”), from Proto-West Germanic *kwakōn, from Proto-Germanic *kwakaną, *kwakōną (“to croak”), of imitative origin. Cognate with Saterland Frisian kwoakje, kwaakje (“to quack”), Middle Low German quaken (“to quack, croak”), German quaken (“to quack, croak”), Danish kvække (“to croak”), Swedish kväka (“to croak, quackle”), Norwegian kvekke (“to croak”), Icelandic kvaka (“to twitter, chirp, quack”).

noun

1. The sound made by a duck.
   Did you hear that duck make a quack?

verb

1. To make a noise like a duck.
   The more breadcrumbs I threw on the ground, the more they quacked.
   Do you hear the ducks quack?
2. (intransitive) Of a queen bee: to make a high-pitched sound during certain stages of development.

Etymology 2

Clipping of quacksalver, from Middle Dutch kwaksalver (“hawker of salve”) (modern Dutch kwakzalver), from quacken (“to brag, boast; to croak”). Ultimately related to etymology one, above.

noun

1. (derogatory) A fraudulent healer, especially a bombastic peddler in worthless treatments, a doctor who makes false diagnoses for monetary benefit, or an untrained or poorly trained doctor who uses fraudulent credentials to attract patients
   That doctor is nothing but a lousy quack!
   1662, Rump: or an Exact Collection of the Choycest Poems and Songs Relating to Late Times, Vol. II, by ‘the most Eminent Wits’ Tis hard to say, how much these Arse-wormes do urge us, We now need no Quack but these Jacks for to purge us, …
   After ſome Months, the Quack gets privately to Town, … 1720, William Derham, Physico-theology
   Polly (to security guard, referring to Dr. Feingarten): Are you going to let that shyster in there? Dr. Feingarten: I could sue you, Polly. A shyster is a disreputable lawyer. I'm a quack. 1981, S.O.B. (film)
   "I don't want to get into specifics, but when I was born, my parts were considered... ambiguous. The quack of a doctor that delivered me, had trouble assigning a gender. So at his recommendation - and surgical intervention - I was raised as a boy." 1 March 2017, Jocelyn Samara D., Rain (webcomic), Comic 920 - Quack
2. (figurative, derogatory) Any similar charlatan or incompetent professional.
3. (humorous slang, mildly derogatory) Any doctor.
   That quack wants me to quit smoking, eat less, and start exercising. The nerve!

verb

1. To practice or commit quackery (fraudulent medicine).
   […] it is incredible, and scarce to be imagin’d, how the Posts of Houses, and Corners of Streets were plaster’d over with Doctors Bills, and Papers of ignorant Fellows; quacking and tampering in Physick, and inviting the People to come to them for Remedies; 1722, Daniel Defoe, “A Journal of the Plague Year”, in et al., London: E. Nutt, page 36
2. (obsolete) To make vain and loud pretensions.
   Seek out for Plants with Signatures To Quack of Universal Cures 1684, Samuel Butler, Hudibras, London, Part 3, Canto 1, p. 18

adj

1. Falsely presented as having medicinal powers.
   Don't get your hopes up; that's quack medicine!
   In precisely the same way does a quack doctor prescribe his infallible nostrum to every patient, without taking into account differences of constitution, or … 1833, James Rennie, “The Word Gardening”, in Alphabet of Scientific Gardening for the Use of Beginners, London: William Orr, page 2
   [R]ecently I examined as many newspapers and magazines as I could lay hands on just to see if I could find in them those old, alluring advertisements, ranging from the quack doctor to the quacker promoter and the quackest oracle of fate. There was nothing doing—everything as clean as a hound's tooth and as wholesome as sunshine. 5 August 1916, Henry D. Estabrook, “Truth in Advertising [advertisement]”, in The Duluth Herald, volume XXXIV, number 102, Duluth, Minn.: The Herald Company, →OCLC, page 6
   Finding, perhaps, that there is no solution either in politics or in any existing religion, he [the common man] may cling to the diagnosis of the last and quackest of his doctors: he may believe that art can save himself and the world. 1948, The Prospect before Us: Some Thoughts on the Future, London: Sampson Low, Marston & Co., →OCLC, page 102
   When no certain cure exists, quack remedies tend to proliferate and the history of quackery and secret cures is full of extraordinary forms of treatment for the various arthritic disorders. 1976-03-27, F. Dudley Hart, “History of the treatment of rheumatoid arthritis”, in British Medical Journal, volume 1, number 6012, →DOI, →JSTOR, page 763
   They desperately want to believe something will help and for that reason they assist one another in obtaining unproven remedies. Such "helpful" promotion is generally more "quack" than fraudulent in nature. 1991, Journal of the Association of Food and Drug Officials, volume 55, York, Pa.: The Association, →ISSN, →OCLC, page 35
   [William] Hogarth might have felt some sympathy for [Sally] Mapp as an 'irregular' expert besting pomposity, but this is topped by his sheer relish for her as the Quackest Quack of all, and female to boot. In Hogarth's print the dark goddess rules over her court of fools, men who have taken over the ancient realm of women's healing, and now profit from the people's ills and credulity. 1997, Jenny Uglow, “Allegories of Healing”, in William Hogarth: A Life and a World, London: Faber and Faber, page 506