Fen-hlíþ

According to the Old English Dictionary:

-hleoþ, es;

fen-hlíþ

n. [hliþ a declivity, slope] A fen-slope, bank of a fen; păluster clīvas, pălūdis rīpa :-- Scolde Grendel fleón under fenhleoþu Grendel must flee under the fen-slopes, Beo. Th. 1645; B. 820. fen-hliþ