Apparently he added it himself. It stands for no particular name.
It was a recursion joke! (I did post it in the Humor section)
If you substitute "Benoit B Mandelbrot" for the B, you then must do so again for the new "B" - and so on.
Odd... Didn't think I'd have to explain that one
here No worries, it made me laugh, but so do many things which are not funny to others