The authors agree that the surname derives from a nickname formed from the term malfatto (from the Italian male fatto), with the meaning "badly made" and, applied to people, "ugly, ungainly or affected by physical imperfections". Both point to the medieval name Malfatus as the form of origin, documented early in the region of Trentino-Alto Adige.

E. De Felice records the form Malfatus as early as the year 971 in Trentino, and identifies Veneto as the region of predominant presence of the surname.

E. Rossoni broadens the geographical distribution: he notes a main area covering Trentino and western Veneto, and another in the Lucca area. For the variant Malfatto, he identifies a lesser area in that of Rovigo and a more important one in the Alessandria and Genoa areas, with offshoots in the Asti area and in lower Turin. Rossoni also supplies historical examples of its fixing as a surname: in the 16th century the magistrate Malfato Salvadori appears at Riva del Garda, and in 1508 the captain Bortolo Malfato of Padua is recorded in the Cadore, in command of the defence of Cortina d'Ampezzo.