In contemporary terminology, the slur "snake oil salesman" refers to hucksters promoting fake products or philosophies. Its original usage, however, described actual peddlers of (usually phony) variations on snake oil liniment, an established folk remedy used by Chinese laborers building the transcontinental railroad. The workers applied the liniment, which was made from the oil of the Chinese water snake, to ease joint and muscle pain and reduce inflammation. When their American counterparts discovered the liniment's curative properties, word spread and producers of "patent medicines" jumped on the bandwagon with their own versions. Unfortunately, products advertised as genuine snake oil were more likely to contain vegetable oil, mineral oil, or the oil of rattlesnakes or other breeds. So many of the products were completely ineffective that snake oil and its sellers became synonymous with deception.

Snake oil may have been among the most egregious medical frauds of the 19th century America, but it was hardly the only one. Until early 1900s, the patent medicine industry operated virtually without regulation. In the West, where the scarcity of qualified medical personnel further complicated matters, "confidence men" with no medical degrees impersonated doctors and prescribed worthless medicine with impunity. These profiteers -- among them the father of oil magnate John D. Rockefeller Sr. -- sold concoctions laced with alcohol, opium, or cocaine. With these ingredients, the drugs sometimes provided distraction from pain but not a cure. Because of the lax oversight, patients became especially susceptible to roving charlatans touting a "miracle" elixir. The salesmen would enter towns, enlist confederates to fake an illness the potion instantly "cured," sell as much of it as possible, and flee before the ruse was discovered.

Political lobbying and press coverage of patent medicine fraud led to the passage of the Pure Food and Drugs Act in 1906. Several lawsuits led to additional reform, among them one in the 1910s against Clark Stanley, a famous purveyor of snake oil. As for genuine oil from the Chinese water snake, during the past three decades researchers have uncovered some secrets of its success: tests have shown it to be rich in omega-3 fatty acids, which are known to reduce inflammation.