Where does “ऊ” come from?

ऊ (Marathi) comes from Sanskrit यूका, from Proto-Indo-European lewH- — louse.

ऊ (Marathi): head louse

Definitions

Step	Language	Word	Meaning
1	Sanskrit	यूका	a louse
2	Proto-Indo-European	lewH-	louse

ऊ — Etymology, Origin & Word History | Etymology Explorer