The authors agree that the surname goes back to the name of Germanic origin Boso (nominative case) or Bosone (oblique case), documented from the early Middle Ages in the Frankish and later German tradition. The base would be a derogatory nickname derived from *boso, in turn from *bausja- (German böse), with the sense of "proud; bad, wicked; hostile, enemy".

E. De Felice notes that the surname is diffused throughout northern Italy and also in Tuscany. He observes that the truncated forms are mainly Lombard and Venetan, while Bosutti and the Slavic-type patronymic Bosich are typical of Friuli-Venezia Giulia. He adds that Bosio and Bosi, in Liguria and southern Piedmont, may derive from the place name Bòsio, in the Alessandria area, or from Bòsia, in the Cuneo area.

R. Brondolo agrees on the Germanic origin and on the possible connection with place names in the Alessandria and Cuneo areas, and adds as an additional hypothesis a possible derivation from the name Ambrosio.