Beaver = Biibaa (sound it out) but also, rarely, Kairi/Umidanuki (海狸) = Sea Tanuki. A "tanuki" is the Japanese racoon dog, which is neither a racoon or a dog. You might know the animal from Animal Crossing. Tom Nook is a tanuki. Still puzzled w/ the use of "Sea," though. Beavers live in rivers.