Meaning

noun an untrained person who pretends to be a physician and who dispenses medical advice

noun the harsh sound of a duck

verb utter quacking noises

originFrom 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…

Etymology from Wiktionary, CC BY-SA 3.0