A beaver is also an animal in the English language. The etymology of the word you can find following this link:
http://www.bartleby.com/61/37/B0143700.html ETYMOLOGY: Middle English bever, from Old English beofor. See bher-2 in Appendix I.
ENTRY: bher-2
DEFINITION: Bright, brown. 1. Suffixed variant form *bhr-no-. a. brown, from Old English brn, brown; b. bruin, from Middle Dutch bruun; c. brunet, burnet, burnish, from Old French brun, shining, brown. a–c all from Germanic *brnaz. 2. Reduplicated form *bhibhru-, *bhebhru-, “the brown animal,” beaver. beaver1, from Old English be(o)for, beaver, from Germanic *bebruz. 3. bear2, from Old English bera, bear, from Germanic *ber, “the brown animal,” bear. 4. berserker, from Old Norse björn, bear, from Germanic *bernuz. (Pokorny 5. bher- 136.)