"better than a snake oil salesman"

A ‘snake oil salesman’ is a derogatory term used for someone who fraudulently sells goods or services, often unproven medical products or treatments. The phrase is thought to have originated in the Western USA from the liniment which Chinese railway workers used to treat joint pain and other ailments. The concoction was supposedly made from Chinese water snake, but a test of Stanley’s Snake Oil in 1917 revealed it to contain only mineral oil, fat, red pepper, turpentine and camphor.