What does "beaver" mean?

Additional senses

1. 2.A hat, formerly made of the fur of the beaver, but now usually of silk. A brown beaver slouched over his eyes. Prescott.
2. 3.Beaver cloth, a heavy felted woolen cloth, used chiefly for making overcoats. Beaver rat (Zoöl.), an aquatic ratlike quadruped of Tasmania (Hydromys chrysogaster). -- Beaver skin, the furry skin of the beaver. -- Bank beaver. See under 1st Bank.
3. 4.That piece of armor which protected the lower part of the face, whether forming a part of the helmet or fixed to the breastplate. It was so constructed (with joints or otherwise) that the wearer could raise or lower it to eat and drink.