ἀντίδοτον

Antidote comes from Greek antídoton, from anti (against) + didónai (to give) — something given against poison. The word entered Latin as antidotum and English by the 1400s. The concept is older than the word. Ancient Egyptian, Mesopotamian, and Indian medical texts describe remedies for poisoning. But the most famous ancient antidote belonged to Mithridates VI of Pontus, the Black Sea king who fought Rome in the first century BCE.

Mithridates, according to Pliny the Elder, consumed small amounts of poison daily to immunize himself — a practice later called mithridatism. When he was finally defeated by Pompey in 63 BCE and tried to poison himself, the poison did not work. He had to order a guard to kill him with a sword. Whether this story is historically accurate matters less than its influence: the idea of building tolerance through gradual exposure persisted in pharmacology for two millennia.

The concept of specific antidotes — particular substances that counteract particular poisons — is mostly modern. Medieval antidotes were often general: theriac (a paste of dozens of ingredients including opium and viper flesh) was believed to cure all poisons. Theriac was prescribed for everything from plague to snakebite. The idea that one substance could counteract all toxins was wrong, but theriac was sold in pharmacies until the 1800s.

Modern antidotes are targeted: naloxone reverses opioid overdoses, atropine counteracts organophosphate poisoning, N-acetylcysteine treats acetaminophen overdose. The word 'antidote' has also taken on a figurative meaning — an antidote to boredom, to loneliness, to cynicism. Something given against. The metaphor extends easily because the original idea is so clear.