E. De Felice notes that this is a Lombard surname derived from the place name Sormano, a locality in the Como area.

E. Rossoni broadens this information, specifying that the surname is typical of the Milan and Como areas. According to this author, the Counts Sormani of Milan took their surname from the Lombard fief of Sormano —whose Latin name was Suburbanum. Rossoni also documents a presence of the surname in Tresivio, in the Sondrio area, during the 16th century, and in Milan itself in that same period, where Battista Sormani, abbot of the college of notaries, is recorded.