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"remedy counteracting poison," 1510s (earlier in English as a Latin word), from Middle French antidot and directly from Latin antidotum "a remedy against poison," from Greek antidoton "given as a remedy," literally "given against," verbal adjective of antididonai "give in return," from anti- "against" + didonai "to give" (see date (n.1)). Cf. Middle English antidotarie "treatise on drugs or medicines" (c.1400).
antidote an·ti·dote (ān'tĭ-dōt')
An agent used to neutralize or counteract the effects of a poison.