Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "cancettan." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 116.
;part. cancettende; p. cancette; pp. cancetted To laugh aloud or in a cackling manner; cachinnare :-- Mæssepreóst ne sceal lufigean micelne and ungemetlícne cancettende hleahtor nor shall a mass-priest love great and immoderate cackling laughter, L. E. I. 21; Th. ii. 416, 36. v. ceahhetan.