This is a tangent, but snake oil was medicinally effective.
The colloquialism "snake oil salesman" comes from the old scam of confidence men selling a cheap, adulterated (and sometimes drugged) mineral oil as snake oil (based on the Chinese water snake from Chinese traditional medicine). People would pay a premium for what they thought was medicine, only to find out later that the confidence men bamboozled them and skipped town with their money.