'molt' originates from Middle English (variants like 'mouten' or 'molten'), ultimately from older Germanic roots related to words meaning 'to change' or 'to cast off'.

'molt' changed from Middle English forms such as 'mouten'/'molten' and later appeared as 'moult' in British English; the modern American spelling 'molt' is a later variant of the same word.

Initially it meant 'to shed or cast off an outer covering'; over time this basic sense has remained, primarily applied to birds (feathers), reptiles/insects (skin/exoskeleton), and sometimes to hair.