The word "quack" derives from the archaic word "quacksalver", of Dutch origin (spelled kwakzalver in contemporary Dutch), literally meaning "hawker of salve". In the Middle Ages the word quack meant "shouting". The quacksalvers sold their wares on the market shouting in a loud voice.
"Health fraud" is often used as a synonym for quackery, but quackery's salient characteristic is aggressive promotion ("quacks quack!") rather than fraud, greed or misinformation. "Pseudo-medicine" is a term for treatments known to be ineffective, regardless of whether their advocates themselves believe in their effectiveness." (Wikipedia)