The surname Zanetti derives from the proper name Giovanni, one of the most widespread in Italy, whose origin goes back to the Hebrew Yôḥānān, meaning "God has been merciful". Through the dialectal transformations of northern Italy, especially in Veneto and Friuli, Giovanni gave rise to the abbreviated form Zanni, from which numerous surnames originate.

Zanetti is a patronymic form built on this dialectal base, with the suffix -etti, very frequent in the north, which indicates descent or family belonging. Its meaning may therefore be interpreted as "sons of Zanni", that is, descendants of an ancestor called Giovanni.

This type of formation reflects both the strong diffusion of the name Giovanni in medieval Italy, driven by the cult of Saint John the Baptist and Saint John the Evangelist, and the adaptation of the name to the local languages. The surname Zanetti is particularly characteristic of the Italian north-east, where these dialectal forms reached a great diffusion.