|B lymphocyte was named after bursa of fabricius|
Mammals generally do not have an organ “specially” made for development of B cells. We have our lovely bone marrow which is both the site of hematopoiesis and B cell development.
Coincidentally, bone marrow starts with a B as well =D
So historically, the credit for giving B cell it’s name goes to bursa of fabricius.. Not our bone marrow! T_T