Wæl-gim[m]

According to the Old English Dictionary:

es;

wæl-gim[m]

m. The word seems to be an epithet for the sheath of a sword, which is called in the riddle the sword's byrne :-- Byrne is mín (a sword's) bleófág, swylce beorht seomað (-d, MS.) wír ymb ðone wælgim, ðe mé waldend geaf, Exon. Th. 400, 20; Rä. 21, 4. wæl-gimm