Fen-fearn
Bosworth & Toller Anglo-Saxon Old English Dictionary - fen-fearn
According to the Old English Dictionary:
fen-fern, es;
- fen-fearn
- n. The fen or water-fern, flowering fern, the herb christopher, osmund-royal; osmunda rēgālis, Lin. salvia?-Fenfearn salvia, Ælfc. Gl. 42; Som. 64, 8; Wrt. Voc. 31, 19.