E. Rossoni proposes that Diegoli could derive from a diminutive form of the name Diego, of frequent use in the Veneto and the Ferrara area. Its presence is concentrated in the Modena area —especially in Finale Emilia and San Felice sul Panaro— and in the Ferrara area, in localities such as Cento, Sant'Agostino and Ferrara itself.

F. De Laurentiis agrees in noting Diego as the base of the surname, and adds that it is a name of Spanish origin that entered Italy late. According to this author, the oldest Iberian forms, Diaco and Diago, allow it to be traced back to Didacus or Didagus, of medieval Latin, whose ultimate etymology remains without a convincing explanation.