|Origin:||quacksalver 'quack' (16-19 centuries), from early Dutch, probably from quacken 'to quack, talk' + salf 'cure'|
the sound a duck makes
someone who pretends to be a doctor - used in order to show disapproval:
quacks selling weight-loss drugs
3 British English informalMN
You'd better go and see the quack with that burn.