From Wikipedia: Quackery
is the promotion
of fraudulent or ignorant medical practices. A quack
is a "fraudulent or ignorant pretender to medical skill" or "a person who pretends, professionally or publicly, to have skill, knowledge, or qualifications he or she does not possess; a charlatan".
The term quack
is a clipped form of the archaic term quacksalver
, from Dutch: quacksalver
a "hawker of salve".
In the Middle Ages the term quack
meant "shouting". The quacksalvers sold their wares on the market shouting in a loud voice.
Common elements of general quackery include questionable diagnoses using questionable diagnostic tests, as well as alternative or refuted treatments, especially for serious diseases such as cancer. Quackery is often described as "health fraud" with the salient characteristic of aggressive promotion.