'molt' likely originates from Middle English (variants: 'multen', 'mouten' or similar), from an earlier Germanic source related to words meaning 'to change' or 'cast off'; exact origin is uncertain.

'molt' appeared in Middle English as forms such as 'multen'/'mouten' and later stabilized into modern English forms 'molt' (US) and 'moult' (UK).

Initially used for the action of casting off or changing an outer covering, and it has retained that basic sense of 'shedding' into modern usage.