The authors agree that this surname derives from the place name Sant'Agata, a place name very extended throughout Italy with various geographic determinations.

E. De Felice notes that the surname was formed from that place name, present in zones of high frequency such as the provinces of Alessandria, Novara, Piacenza and Bologna in the north, those of Naples, Caserta, Avellino and Benevento in the region of Campania, and those of Messina and Catania in Sicily. He further mentions an apocopated form, Santagà, of Venetan origin. He refers the reader to the entry Agati for complementary information.

E. Rossoni specifies that the surname seems to originate mainly from the Caserta and Naples areas, with an additional presence in the Modena and Bologna areas, and in the strip that extends from the Foggia area to the north of the Cosenza area. He links the surname to specific place names such as Sant'Agata Bolognese, Sant'Agata sui Due Golfi, Sant'Agata di Esaro, Sant'Agata di Puglia and Sant'Agata Irpina.