'turn down' originates from Middle English, specifically the words 'turn' and 'down', where 'turn' meant 'to rotate' and 'down' meant 'toward a lower position'.

'turn' and 'down' were used separately in Middle English and eventually combined to form the modern English phrase 'turn down'.

Initially, it meant 'to rotate downward', but over time it evolved into its current meaning of 'to reject or refuse'.