The authors agree that it is a pan-Italian surname more frequent in Lombardy and in Emilia-Romagna. Its etymological base is the Latin cognomen Bassus, probably of Oscan origin, and also the medieval adjective basso, derived from the Latin bassus ("stout"), with the sense of "short in stature".

E. De Felice documents this use as a nickname from the Early Middle Ages, especially in southern Italy: Leo Bassus, Farfa, 814; Landulfus Bassus, Aversa, 1160. He also notes that the forms Bascio and Basciu are peculiar to the southern region and to Liguria; the patronymic Bassich corresponds to eastern Veneto; and the variants with the article Lo and Li —such as Lo Basso and Li Bassi— are characteristic of the Naples area and the far south of Italy. The form Basciano is also southern, with greater presence in the Naples area.

F. Miranda broadens the picture of variants and includes forms such as Basso, Bassa, Lobasso, as well as derivatives and diminutives: Bassetti, Bassini, Bassolino, Bassotti. He identifies specific areas of presence in the Veneto —in the provinces of Treviso, Vicenza, Venice and Padua—, in Piedmont —in the Cuneo and Turin areas—, and also in Liguria, Lombardy, Friuli-Venezia Giulia, Lazio and Puglia. In Sicily he records its diffusion in the provinces of Palermo, Catania, Syracuse, Messina, Ragusa and Enna.