Why are some mushrooms called toadstools?

The word “toadstool” dates to the Middle Ages when it was associated with the toad, which was thought to be poisonous. Toadstools, with their stool-like shape, are really mushrooms that are poisonous or inedible. For example, the bright red “fly agaric” toadstool's juice was once used to make a remedy for killing bugs. It is a very poisonous mushroom that still lives today and should be avoided.