'banewort' originates from Old English, specifically the elements 'bān' (or 'bana') and 'wyrt', where 'bān'/'bana' meant 'death' or 'slayer' and 'wyrt' meant 'plant'.

'banewort' changed from Old English 'bānwyrt' (or similar compound forms) and through Middle English forms became the modern English word 'banewort' (also attested as 'bane-wort').

Initially, it meant 'a plant that brings death' or 'poisonous plant'; over time the core meaning has largely remained, though use has become archaic and occasionally figurative ('a cause of ruin').