Traht-bóc

According to the Old English Dictionary:

traht-bóc

f. A book of exposition, a treatise, commentary :-- Gregorius gedihte manega hálige trahtbéc, Homl. Th. ii. 132, 15 : i. 436, 10. Twá and hundseofontig bóca ðære ealdan ǽ and ðære níwan hé áwende . . . búton óðrum menigfealdum trahtbócum ðe hé deópðancollíce ásmeáde, 15. traht-boc