--not literally, but because that became a shorthand slang for rip-off substances, sold with great hype, that were supposed to effect medical "cures".

In the old American West, one of the numerous ingredients that were supposed to be in these "tonics" and other formulations was snake oil, hence the term. Over time it came to be used to mean any substance that purported to give relief or cure that was just an unscrupulous attempt to prey on the vulnerable and which has nothing in it that could actually help.