Ymb-set

According to the Old English Dictionary:

es;

ymb-set

n. Siege, blockade :-- Ðæt gér ymbsetes ðære Beadonescan dúne annum obsessionis Badonici montis, Bd. 1, 16; S. 484, 22. Hé ne mihte ne mid gefeohte ne mid ymbsete (obsidione) ða burh ábrecan ne gegán, 3, 16; S. 542, 19. [O. H. Ger. umbi-sez obsidio.] ymb-set