Losa seems to be typical of the area between Bergamo, Lecco and Milan, Lossa, absolutely extremely rare, it would seem either Lombard or Piedmontese, it is however an ancient surname since in 1580 we find in Turin a certain Losa Bartolomeo as representative of the city and, in 1640 the Cav. Aleremo Losa. It could derive from the dialectal word losa (stone) or from the apheresis of toponyms like Mandolossa (BS).
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