Be-seóþan

According to the Old English Dictionary:

be-seóþan

to boil away, reduce by boiling :-- Wæter besoden oþ þone þriddan dǽl, Lch. ii. 188, 16. Seóþ þú hyt swá swíðe þat se þridda[n]-dǽl beó besodan, iii. 92, 19. be-seoþan