Where does “Mosa” come from?

Mosa (Italian) comes from Latin Mosa, from Celtic Mosa, from Proto-Celtic Mosā.

Ancestry of “Mosa”, step by step

Step	Language	Word	Meaning
1	Latin	Mosa	Meuse River; the river Meuse
2	Celtic	Mosa	—
3	Proto-Celtic	Mosā	—