'moult' originates from Middle English, specifically the word 'mouten', where the root is uncertain but carried the sense 'to change or cast off'.

'moult' changed from the Middle English word 'mouten' and eventually became the modern English word 'moult' (with variant spelling 'molt' in American English).

Initially it meant 'to cast off or change an outer covering', and over time it has retained that basic meaning, referring specifically to feathers, hair, or skin.