'poison' originates from Old French, specifically the word 'poison' (meaning 'a drink, potion'), ultimately from Latin 'potio' (from 'potare' = 'to drink').

'poison' came into Middle English from Old French 'poison', which derived from Latin 'potio'/'potionem'; the meaning shifted from 'a drink or potion' to 'a harmful substance' over medieval usage.

Initially it meant 'a drink or potion' (often medicinal); over time it evolved into the current meaning of 'a substance that can cause illness or death' and related figurative senses.