antidote (n.) Look up antidote at Dictionary.com
"remedy counteracting poison," early 15c. (c. 1400 as a Latin word in English), from Middle French antidot and directly from Latin antidotum/antidotus "a remedy against poison," from Greek antidoton (pharmakon) "(drug) given as a remedy," from antidoton literally "given against," verbal adjective of antididonai "give for" (also "give in return, give instead of") from anti "against" (see anti-) + didonai "to give" (from PIE root *do- "to give"). Compare Middle English antidotarie "treatise on drugs or medicines" (c. 1400).