No. Fen is a common, although obscure, noun and doesn't require a capital letter.
Fen. As in Fenway Park being on the road that is the way to the fen.
from the crossword puzzle in social studies or science
"B" is the chess annotation for Bishop.In FEN notation the letter as a capital indicates a white piece, in lower case it indicates a black piece. so 'B' or 'b'.
Fen
Fen
fan, fen, fun or fin
fen phen
Fen Drayton's population is 827.
The population of Borough Fen is 130.
Gervase Fen was created in 1944.
The population of Fen Ditton is 747.
Yao Fen was born in 1967.