出典:Wiktionary
From Proto-West Germanic *wītagadōm. Cognate with Old High German wīzagtuom. By the literary period equivalent to wītiġ + -dōm, but probably formed originally from the etymons of wītga + -dōm; wītiġdōm is the expected outcome either way. Compare lǣċedōm (“medicine”), which is formed similarly.