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 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.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. ""Health fraud"" is often used as a synonym for quackery, but quackery's salient characteristic is its more aggressive promotion (""quacks quack!""). ""Pseudo-medicine"" is a term for treatments known to be ineffective, regardless of whether their advocates themselves believe in their effectiveness.