'crooked-legged' originates from modern English, specifically the compound of 'crooked' and 'legged'. 'crooked' comes from earlier English words meaning 'bent' or 'hooked', and 'legged' is formed from 'leg' with the adjectival suffix '-ed' meaning 'having legs'.

'crooked' developed from Old and Middle English forms related to words for 'hook' or 'bend' (e.g. Middle English 'croked'/'crook'), and 'leg' has been present in Old English with a similar meaning; the compound 'crooked-legged' is a straightforward modern English formation combining these elements.

Initially the components meant 'bent/hooked' (for 'crooked') and 'lower limb' (for 'leg'); over time the compound came to mean 'having legs that are bent or not straight', which is its current usage.