Most likely to fail to look before they leap round these parts are toads. Toad, according to the Online Etymology Dictionary, comes from Old English, but nobody knows how it got there. There's no evidence it comes from any of the usual parents like Latin or German, and there aren't any similar words in any other language. It's surprising to me, actually, how rarely I run across a word that seems to have come from nowhere. I mean, every word in every language exists because somebody made it up. So how come so many words seem to have been made up by English-speakers? Other than the fact that English is kind of a young whipper-snapper compared to other languages. Why make up new words for things for which perfectly good words exist already?
Leading me to conclude that toads did not exist until after English was born. Makes perfect sense to me.
Toadstool comes from around the 14th century. Seems toads back then were considered very poisonous, and toadstool typically refers to toxic mushrooms. So a toadstool is poisonous like a toad and shaped like a stool.
Toads do not give you warts, as you probably knew. I know that toads don't cause warts, was never led to believe that myth was true, far as I know. Yet I still get a little ookie when I have to rescue one from the porch, moreso than when I have to rescue frogs.
If a toad is poisonous, by the way, the poison will be secreted by the warts, which aren't actually warts, according to HowStuffWorks.com, but glands. So even though the warts aren't warts and don't give you warts, it's probably still not a good idea to touch them. Or lick them. Don't lick toads, kids.