'bow-legged' originates from Old English and related Germanic roots: 'bow' (Old English 'boga') meaning 'arch' or 'curve' and 'leg' (Old Norse 'leggr' / Old English 'lēg') meaning 'leg', combined with the adjectival suffix '-ed'.

'bow-legged' developed as a compound in Middle to Early Modern English (earlier spellings and compounds such as 'boge-legged' or 'bowlegged' have been recorded) and eventually became the modern hyphenated form 'bow-legged'.

Initially it described legs shaped like a bow ('having a bowed shape'); over time the meaning has remained essentially the same, describing an outward curvature of the legs.