E. Rossoni and F. Miranda agree that this surname, together with its variant Testaì, derives from the trade of potter or maker of vessels practised by the original family stem. The etymological base is the Latin testum / testa, words with which vessels or containers, generally of terracotta, were designated; hence testai would be equivalent to "vessel-makers".

As for geographical distribution, both authors agree in noting the presence of the surname in Sicily —especially in the Catania, Enna and Palermo areas— and in Tuscany, between the Pisa and Livorno areas. Miranda adds that there is also a presence in the Trapani area, and that with less consistent nuclei the surname appears in Lombardy, Piedmont, Emilia-Romagna, Liguria, Lazio and Campania.

Rossoni further specifies that the surname presents two independent stems of origin (ceppi): one in the Catania, Enna and Palermo areas, and another in the Pisa and Livorno areas. As for the variant Testaì, rarer, Rossoni places it between the Enna and Catania areas, while Miranda mentions it as a variant of the same surname without specifying its particular geographical distribution.