It is common in the Middle Ages for criminals to go around villages pretending to be doctors so they can sell fake medicines. They hold demonstrations in the village square where they miraculously “cure” their assistant of an illness. The most popular demonstration is for the assistant to swallow a toad – because in those days ordinary people thought that toads were full of deadly poison. The “toad eater” will then roll around the floor pretending to be sick (not much acting will be required) and then the “doctor” will give you a medicine which “cures” you. The local villagers will then (hopefully) be convinced that the doctor is genuine and queue up to buy his medicines! It is from the phrase “toad eater” that we still have the word “toady” meaning someone who sucks up to people.