For other uses of the word bane, see bane (disambiguation).

The meaning of bane as an English form of nemesis, the bringer of ruin, dates only from 1577. Now an affliction, curse, evil, ill, plague, scourge or woe, in Old English bana had a more specific and immediate meaning, of "slayer", "murderer."

In the Middle Ages, a number of plants were thought to have poisonous or prophylactic qualities, which would have dire consequences (Henbane) or liminal ones, like "Wolfsbane" ("Aconite", Aconitum). Aconite is thoroughly poisonous, but no one would bait a wolf-trap with it. So its qualities of a "bane" must be protective, for the wolf is more dangerous than a mere ravening carnivore. Many medieval Europeans believed that they could become a werewolf. Aconite was the toxic entheogen that could keep the dire transformation from happening. Milder poisoning, at a later date, was thought to trouble sheep in the U.S. southeast, if they strayed into woodland and nibbled Kalmis latifolia , or "sheep's bane").