Where does “nuba” come from?

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

Ancestry of “nuba”, step by step

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