Fen-gemirce

According to the Old English Dictionary:

(?), es;

fen-gemirce

n. The boundary of marsh-land:--Þis sint þá fangemerca . . . tó binguuellan æt clibe út on ðone bróc midne, suǽ. . . út on mór . . . þanon andlangæs bróces middesweardes, C. D. B. i. 295, 27. fen-gemirce