The authors agree that Pisani is a surname of toponymic origin, derived from the name of the city of Pisa, in the region of Tuscany. Its original meaning is 'those of Pisa' or 'the one who comes from Pisa', a form of identification by provenance very common in the Middle Ages: when someone moved to another city, they could be called il Pisano or Pisani, a designation that in time became fixed as a hereditary surname.

F. Miranda adds that the surname is of the ethnic type and specifies that the place name Pisa has two possible etymologies according to the ancient sources: Pliny considers it founded by the Teuti or by Pelops, king of the Pisei, thirteen centuries before Christ; other historians, on the other hand, propose an Etruscan origin, derived from pise, 'river mouth'.

As to its diffusion in Italy, Miranda notes that the surname is present in around a thousand municipalities, with a greater concentration in Campania, Lombardy, Tuscany, Apulia, Lazio and Calabria, and smaller specific areas in Veneto, Piedmont, Liguria, Sicily, Emilia-Romagna and Basilicata. In Sicily it appears with greater density in the Ragusa area —especially in Scicli, Vittoria and Ragusa—, with relevant presences also in the Messina, Catania and Palermo areas and in the comune of Regalbuto, in the Enna area. It is further considered that the surname had an early diffusion in Sardinia, linked to the historical contacts of that island with the Italian peninsula.

Among the variants of the surname are recorded: Pisano (a demonym, frequent in Tuscany, Campania and southern Italy), Pisanello (a diminutive form of southern Italy), Pisanelli (a patronymic form of the centre and north), Pisanò (a dialectal variant of the Salento area —the southernmost zone of Apulia, in southern Italy—), Pisanu (a local adaptation proper to Sardinia) and Pisaneschi (a less frequent regional variant of Tuscany).