To Alexey Sklyarenko: I must report the prosaic fact that "beaver" is
obsolete slang for "beard" or "a bearded man".
Thank you, Jerry, for letting me know this. I
should have consulted my Random House Webster. It is not as big as Webster's
Second but does cite, too, "beaver" as meaning "beard" or "bearded
man" (as well as being vulgar slang for "a woman's pubic area").
Still, I think that Nabokov had also in mind the castor/Castro connection.
It looks too Nabokovian. Btw., I seem to recall that Castro grew his beard in
honor of Marx whom he studied when hiding in Mexican forests in the late 1950s.
Somewhere VN refers to Castro as "that bearded man from Cuba" (or similar
words).
best,
Alexey