Origin and history of toad

"stone or stone-like object, supposedly magical (with healing or protective power) and found in the heads of certain toads," 1550s, from toad + stone (n.). Translating Greek batrakhitēs, Medieval Latin bufonites; compare also French crapaudine (13c.), German krötenstein.

The Crapadine or Toadstone, we speak of before, you shall prove to be a true one, if the Toad lift himself so up against it, when it is shew'd or held to him, as if he would come at it, and leap to catch it away: he doth so much envy that Man should have that stone. ["Eighteen Books of the Secrets of Art & Nature," 1661]

late 14c., tode-stole, a common name for umbrella-shaped fungi; it is apparently a fanciful name from Middle English tadde "toad" (see toad) + stole "stool, seat" (see stool). Toads themselves were regarded as highly poisonous, and since c. 1800 this word is "popularly restricted to poisonous or inedible fungi, as distinct from edible mushrooms" [OED, 1989]. Compare toad-cheese, a poisonous fungi. In Promptorium parvulorum (mid-15c.) Middle English toodys hatte glossed Latin boletus. Toad's meat (1886) was, a rustic term for "toadstool."