'sine' originates from Latin, specifically the word 'sinus', where 'sinus' meant 'bay, fold, or curve'.

'sine' changed from Sanskrit 'jya' (a term for a chord) to Arabic 'jiba' (جَيْب), which was rendered in Medieval Latin as 'sinus' and eventually became the modern English word 'sine'.

Initially, it meant 'bend, bay, or fold' in Latin usage, but over time it evolved into its current mathematical meaning as the trigonometric ratio (opposite/hypotenuse).