Wikipedia tells us that Snake oil is an expression that originally referred to fraudulent health products or unproven medicine but has come to refer to any product with questionable or unverifiable quality or benefit. Read more here https://en.wikipedia.org/wiki/Snake_oil.
I do like this tale (found at Wikipedia)
The composition of snake oil medicines varies markedly among products.
Stanley’s snake oil — produced by Clark Stanley, the “Rattlesnake King” — was tested by the United States government in 1917. It was found to contain:
- mineral oil
- 1% fatty oil (presumed to be beef fat)
- red pepper
This is similar in composition to modern-day capsaicin-based liniments or chest rubs. None of the oil content was found to have been extracted from any actual snakes. The government sued the manufacturer for misbranding and misrepresenting its product, winning the judgment of $20 against Clark Stanley. Soon after the decision, “snake oil” became synonymous with false cures and “snake-oil salesmen” became a tag for charlatans.