Where does “nubilum” come from?

nubilum (Latin) comes from Latin nūbilus, from Latin -idus, from Proto-Italic *-iðos.

Ancestry of “nubilum”, step by step

Step	Language	Word	Meaning
1	Latin	nūbilus	—
2	Latin	-idus	tending to
3	Proto-Italic	*-iðos	—