The surname Bertoldi and its variants —such as Bertoldo— have an anthroponymic origin linked to Germanic names spread in medieval Italy. According to E. De Felice, they derive from the personal name Bertòldo or Bertaldo, documented between the 11th and 12th centuries in Latinised forms such as Bertoaldus, Bertaldus and Bertoldus. This name is composed of the Germanic elements berhta- ("bright, illustrious") and waldaz ("powerful, chief"), meaning "illustrious and powerful", typical of the Germanic onomastic tradition.

From the point of view of diffusion, E. De Felice notes that the surname is present in northern Italy, although it is particularly frequent in the Veneto and, above all, in Trentino in the form Bertoldi. This regional concentration suggests a local development from this medieval name.

For his part, E. Rossoni confirms this origin in the Lombard name Bertholdus, documented in the 12th century, and mentions examples of its transformation into a surname as early as the 13th century in the Cividale area (Udine). He adds that Bertoldi is spread throughout the centre-north, probably with origin in western Veneto and Trentino, while Bertoldo presents clusters in areas such as Cuneo, northern Milan and eastern Veneto. Taken together, both interpretations agree in pointing to a Germanic origin with a well-defined regional evolution in northern Italy.