The authors agree that this surname is of Germanic origin and is especially rooted in Trentino. It derives from the Middle High German term mos or the German Moos, which means "marsh" or also "moss", and originally designated one who lived near marshy ground, a designation that in time became a surname. This form is also proper to southern Germany, Austria and Switzerland.

E. De Stefani notes that in Trentino the surname is concentrated especially at Trento and Pergine Valsugana, and that in Carnia —the mountainous region of northern Friuli, in the Udine area— it is documented at Paluzza from at least the beginning of the 17th century. He adds that the same Germanic base mos(a) left traces in the local toponymy, such as the place called Mosa at Pesariis and the place name Moss at Sappada.

E. Rossoni proposes that the surname could also derive from the place name Moso in Passiria, in the Bolzano area, or have been formed directly from the Austrian surname Moser. He specifies that its original core in Trentino is linked to the marshy territory that existed south of Miola, a hamlet of Baselga di Piné, from where —in particular from Faida and Miola— the surname spread throughout the region.