1911 Encyclopædia Britannica/Moult

MOULT, a term for the shedding of feathers at the periodic renewal of the plumage by birds, and so transferred to the periodic shedding of the old skin, shell, &c., by other animals. The word is seen in O. Eng. in the verb bimútian, to exchange; from Lat. mutare, to change; cf. mod. Ger. mausen, mausern; the earlier forms in English are mout, mute; the insertion of the l, as in “fault,” dates from the 16th century.