Answer:
Quackery is the promotion of fraudulent or ignorant medical practices. A quack is a "fraudulent or ignorant phony person who claims to possess medical knowledge" or "a person who pretends, professionally or publicly, to have skills, knowledge or qualifications that he does not possess; a charlatan ».
The word quack derives from the archaic word of Dutch origin quacksalver (written "kwakzalver" in contemporary Dutch), literally "peddler of pomade." In the Middle Ages the word quack meant "to shout". The quacksalvers sold their merchandise in the market, loudly proclaiming it.
"Health fraud" is often used as a synonym for quackery, but the most notable feature of the latter is its more aggressive promotion (quacks quack !, "quacks do quack!"). Pseudomedicine is a term for ineffective treatments demonstrated, regardless of whether its advocates really believe in its effectiveness.