Fyrenum

According to the Old English Dictionary:

fyrenum

adv. [dat. pl. of fyren a sin, crime] Sinfully, criminally; măle, sceleste :-- Bona of flánbogan fyrenum sceóteþ the slayer wickedly shoots from his arrow-bow, Beo. Th. 3493; B. 1744. Fyrenum gesyngad criminally perpetrated, 4874; B. 2441. fyrenum