The consulted works concur in tracing this surname to a Germanic root connected to the personal name Maino, itself related to the element magin- (from magan-: "strength, power"). It is also considered a surname derived directly from that Germanic given name.

E. De Felice specifies that Maino is a name of Germanic origin already attested in the Lombard and later the Frankish period. It may function either as an autonomous name formed from magin- or as a hypocoristic reduced to the first element of compound names sharing that same root. De Felice further notes that the related form Mainetto admits additional explanations: it could derive from the Old French Mainet, which spread in Italy through the Carolingian epic, or, in central Liguria, reflect the place name Mainetto in the municipality of Serra Riccò.

V. Blunda stresses the Sicilian character of the surname and observes that the antepenultimate stress of the form Máino is characteristic of the personal-name traditions of certain regions of northern Italy, where archaic stress patterns were preserved. Blunda also notes that the surname survived especially in Alpine and pre-Alpine areas, where Germanic anthroponymy had formed a dense onomastic substratum from the Lombard period through the late Middle Ages. The sources further record a connection to the personal name Mainold, interpreted as "he who rules the people," with a documented presence in the area of Bergamo.

The surname is found with greatest frequency in Lombardy and Emilia-Romagna.