The surname Zaghi is interpreted, according to the main scholars, from several possible ways of formation. E. Rossoni notes that it could derive from the loss of the initial syllable in various place names of northern Italy, such as Massanzago (Padua), Lorenzago (Belluno), Cazzago (Venice), Vanzago (Milan) or Sozzago (Novara). In this case, the surname would have arisen as an abbreviated form indicating geographical provenance, a fairly frequent phenomenon in the evolution of Italian surnames.

The same author also mentions another possible interpretation linked to dialectal use: in Venetan, zago designates a cleric or altar boy, which suggests an occupational or descriptive origin for some lineages. He also provides historical documentation, such as the figure of the painter Antonio Zago, active in the Venetan sphere in the second half of the 15th century, which confirms the antiquity and diffusion of the name in that region.

For his part, F. De Laurentiis considers Zaghi simply a variant of Zago, which reinforces the idea of a phonetic evolution within the same group of surnames. As a whole, the surname Zaghi reflects a complex formation, which can be linked both to abbreviations of place names and to dialectal terms, within the linguistic context of northern Italy.