Where does “fossatum” come from?

fossatum (Latin) comes from Latin fossa, from Latin fodiō, from Proto-Indo-European bʰod- — to pierce, dig.

Ancestry of “fossatum”, step by step

Step	Language	Word	Meaning
1	Latin	fossa	ditch, trench, moat; gutter, waterway; grave
2	Latin	fodiō	—
3	Proto-Indo-European	bʰod-	to pierce, dig