Reconstruction:Proto-Germanic/Masō

Etymology
From a language, presumably. Despite the obvious similarities, the name is not derived from 🇨🇬. It shows evidence of the change from of o to a; this is known to have occurred before the first contact of Germanic people with the Romans, but probably after first contact with the Celts. Most likely, Latin and Germanic both borrowed the name from Celtic independently.

Albrecht Greule writes that its ultimate origin is unclear, but could perhaps be 🇨🇬, whence 🇨🇬 and 🇨🇬. Or, from in the sense of the river's tortuousness, cognate with 🇨🇬 (modern 🇨🇬), 🇨🇬, 🇨🇬.

Proper noun

 * 1)  the river Meuse