'anteflexed' originates from Latin, specifically from elements found in Late Latin such as 'ante-' and forms related to 'flectere' (e.g. 'anteflexus'), where 'ante-' meant 'before' and 'flectere' meant 'to bend'.

'anteflexed' developed via Late/Medieval Latin forms (for example Late Latin 'anteflexus' or Medieval Latin 'anteflexio') and entered English usage in medical/anatomical contexts as 'anteflexion'/'anteflexed'.

Initially it meant 'bent forward' in Latin-derived medical usage, and over time it has retained that core meaning in modern English anatomical contexts.