The authors agree that the surname admits several hypotheses of origin. One links it to the Latin cognomen Granatus, noted by E. Rossoni. Another hypothesis, shared by both authors, derives it from the Latin granatum malum ("apple full of seeds"), that is, the fruit of the pomegranate tree, and relates it to someone who grew or sold pomegranates, or else to a nickname for someone with reddish hair or complexion. They also agree on a possible toponymic origin: the locality of Granata, a hamlet of the comune of Santa Maria del Cedro, in the Cosenza area; Mount Granata, in the Foggia area; or the Spanish city of Granada. Rossoni further adds the Spanish term granado, with the sense "strong, notable".

As for geographical distribution, Rossoni notes that the surname is found throughout Italy, and that the variant Granato is proper to southern Italy, with a significant presence in Campania. F. Miranda specifies that, although the surname appears in every Italian region, the specific areas of greatest concentration lie in Lombardy —especially in the Milan, Lodi and Pavia areas—, in Campania —in the Naples, Caserta and Salerno areas— and in Sicily, with a notable presence in the Catania, Messina, Palermo and Syracuse areas.