Where does “nūbila” come from?

nūbila (Latin) comes from Latin nūbēs, from Proto-Indo-European (s)newdʰ- — to cover.

Ancestry of “nūbila”, step by step

Step	Language	Word	Meaning
1	Latin	nūbēs	—
2	Proto-Indo-European	(s)newdʰ-	to cover