@Ionus,
Everything I said was correct, you seem to be humor challenged (a common occurence with the uneducated). When I accused you of mispronouncing Biber as Fiber due to your OVERBITE, I was referring to your squirrel w/ a machine gun avvie. However , you seem so damned touchy with people you fear , you miss all attempts at humor.
Biber IS german fro brown beaver.
CAstor is the generic name that was chosen for ALL beavers in the world. (The latin word "fiber" actually means more like "BROWN" , so its not a true descriptor of the animal. Thats why the binomial nomenclature has established the names of the species
NorthAmeircan is called CASTOR canadensis, (now you dont think that Canadensis means beaver do you?)
Castor fiber is the "brown beaver of Eurasia"
Ancient beavers were given totally different generic names and only the,last (of the megafaunal kinds) like CAstor Ohioensis were even of the same genus.
The species name is usually a descriptor(an adjective of the genus propwer). So it is with Castor fiber. the fact that it has a latin root means that the etymologist you read, didnt complete his homework thats all.