The surname Betti and its numerous variants —such as Bettini, Bettin, Betto, Bettinelli or Bettoni— are spread in central-northern Italy, with special presence in Tuscany and Emilia, and truncated forms typical of the Veneto. According to E. De Felice, its origin goes back to the affectionate and familiar name Betto (and its feminine Betta), which can be interpreted in various ways: as a contraction of Benedetto, as an aphaeresis of names such as Iacobetto or Zanobetto, or as the continuation of the Germanic hypocoristic Betta (derived from Berto). In some cases, the feminine Betta can also come from Elisabetta. This multiplicity of origins explains the great variety of forms developed over time.

Along the same lines, F. De Laurentiis confirms both the wide diffusion of the surname in the centre-north and the base in the names Betto and Betta, stressing their affectionate and familiar character. He also agrees on the diversity of possible derivations: from Benedetto to abbreviated forms of other names or Germanic hypocoristics. This agreement between authors reinforces the idea of a complex anthroponymic origin, in which different linguistic and cultural traditions converge.

For his part, E. Rossoni broadens the picture by noting that these surnames could derive from affectionate, augmentative or patronymic modifications of the medieval name Bettus, documented as early as 1180 in Lombardy. He also proposes possible connections with Germanic roots (bertha, "luminous") or Celtic ones (bert, "bearer"), as well as with abbreviated forms of Benedetto in dialect. He also provides a detailed regional distribution: Betti predominates in Tuscany, Umbria, the Marche and Lazio; Bettin and Betto are typical of the Veneto; Bettinelli and Bettoni of Lombardy. Taken together, the various interpretations show a surname of diverse origin, deeply rooted in the medieval onomastic tradition.