According to Robert Graves, in a piece I read many years back, the term "toadstool" derives from the fact that a toad whan attacked or frightened, excretes from its back the active chemical in "amanita muscaria." Toxic, but not lethal in lesser amounts.

Siberian Eskimos, desirous of the strong hallucinations derived from thei fungus would feed it to reindeer and then drink the urine, the toxins having been filtered out.