'sinuously' originates from Latin, specifically the adjective 'sinuosus', which comes from 'sinus' meaning 'bend, curve, fold'.

'sinuous' came into English from Latin 'sinuosus' (meaning 'full of folds, winding') via Late Latin/Medieval Latin forms; the adverbial suffix '-ly' was later added to form 'sinuously'.

Initially, it referred literally to physical bends or folds (from 'sinus' = 'bend, curve'), but over time it has broadened to describe both physical winding forms and figurative indirectness or graceful, curving movement.