According to E. Rossoni, the surname is interpreted as a patronymic form typical of the Venetan sphere, with the ending -ato in the sense of "son of". It would derive from a dialectal form with the loss of the initial syllable (aphaeresis) of a diminutive of the name Giovanni, in line with other variants such as Zanni or Zan. In addition, historical records of families with this surname —such as the Zanirato— are documented in the Rovigo area from the second half of the 18th century, which confirms its regional rooting. For a more complete understanding of the origin and evolution of this group of surnames, it is advisable to consult also the entry dedicated to Giovanni.

For his part, F. De Laurentiis considers it simply a derivative of Zanni, a widely diffused hypocoristic form of Giovanni, which reinforces its patronymic character within this large set of surnames linked to one of the most widespread names of the Italian tradition.