BEAVER, the lower part of thehelmet (q.v.) fixed to the neck armour to protect the face and cheeks ; properly it moved up wards, as the visor moved down, but the word is sometimes used to include the visor. The right form of the word, "baver," has been altered from a confusion with "beaver," a hat made of beaver-fur or a silk imitation, also, in slang, called a "castor," from the zoological name of the beaver family.