F. Miranda and G. P. Holmes agree that the surname Grasso originated as a nickname referring to the physical appearance of the original bearer. The name derives from the Latin crassus (“thick,” “stout”) and the medieval form grassus, terms used to describe a corpulent or well-built person.

According to F. Miranda, the surname may originally have been applied to someone who was overweight, physically robust, of a strong or coarse temperament, or even a person who enjoyed a comfortable standard of living. Such descriptive nicknames were common in medieval Italy and frequently became hereditary surnames over time.

G. P. Holmes adds that, in historical contexts, stoutness was often associated with strength, prosperity and good health. For this reason, the nickname may not always have carried a negative meaning; in many cases it likely conveyed a positive or even auspicious image of vigor and well-being.

Today, Grasso is widespread throughout Italy, with particularly strong concentrations in Sicily, Campania, Piedmont, Lombardy and Apulia. In Sicily, where the surname is especially common, it is found in virtually every province, with notable clusters in the areas of Messina, Catania, Palermo, Syracuse, Trapani, Agrigento, Caltanissetta and Enna.