A bezoar is a mass similar to a stone taken from the stomach of a goat, and can be used as an antidote to many poisons, one exception of note is basilisk venom, which a bezoar will not be helpful.
As a bezoar is a biological item, they have existed for as long as goats have existed. Their use in potions predates written history, and as such it cannot be determined when the wizarding world started using them. The bezoar is a small object made of particles that cannot be digested, such as hair, plant fibre, or other indigestible matter. Bezoars are taught about in Potions class, and due to their use as an antidote to many common poisons are taught about in the first year at Hogwarts, although they show up from time to time throughout a students time in school.
From the Persian “pâdzahr,” which literally translates to “protection from poison.”