'blood-poisoned' originates from Modern English, a compound of 'blood' and the past participle of 'poison'; 'blood' comes from Old English 'blōd' meaning 'blood', and 'poison' comes via Old French 'poison' from Latin 'potio' (originally 'a drink').

'poison' changed from Latin 'potio' to Old French 'poison' and entered Middle English as 'poison'; the compound 'blood-poison' (meaning to cause poisoning of the blood) and its past participle 'blood-poisoned' developed in Modern English by combining these elements.

Initially 'potio' meant 'a drink' in Latin and later came to mean 'a drink that harms' (poison); over time the combined form came to mean 'to cause poisoning of the blood' and the adjective 'blood-poisoned' denotes a state of blood infection.