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-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”).
- The sound made by a duck.
- Did you hear that duck make a ?
c 1630, clipping of quacksalver, from Middle Dutch kwaksalver (“hawker of salve”) (Dutch kwakzalver), from quacken (“to brag, boast; to croak”)
- A fraudulent healer or incompetent professional, especially a doctor of medicine; an impostor who claims to have qualifications to practice medicine.
- A charlatan.
- (slang) A doctor.