The authors agree that the surname derives from a nickname related to the blond colour of the hair and, in some cases, of the beard or the light complexion of the ancestor who originated it, later becoming a surname from the Italian adjective biondo.

E. De Felice notes that the surname is spread throughout Italy, although he specifies that the variants Biundo and Biunno, Blundo and Blunno, as well as the compound Biondolillo, are peculiar to southern Italy, while Brundu corresponds to Sardinia. These forms reflect dialectal adaptations of the adjective biondo: the forms biùnno and blundo or blunno in the south, and brundu in Sardinia.

F. Miranda goes deeper into the etymology of the term and notes that its origin is disputed. Many authors trace it to the Germanic blund, but Devoto argues instead for a Lepontic (Celtic) provenance, with subsequent passage into Vulgar Latin blundus. The most accepted hypothesis is that of the Old French blond, from which both the Spanish blondo and the Italian biondo would derive.

Miranda also indicates that the surname appears throughout Italy, with a more marked presence in the central-northern regions, such as Tuscany, Emilia-Romagna, Lombardy, the Marche and Lazio, followed by Campania, Sicily, Piedmont, Abruzzo and Liguria, among others.