E. De Felice and E. Rossoni differ on the origin of the surname.

E. De Felice derives it from the place name Perosa, frequent in northern Italy (Perosa Argentina and Perosa Canavese, in the province of Turin, among others).

E. Rossoni, on the other hand, notes that its origin is difficult to establish. Perossa is specific to Trieste and to Muggia, in the Trieste area, and according to local documentation its ancestor was a certain Iacomo de Petroxa, documented in 1426. He proposes that Perossa is a matronymic of the old feminine name Petrossa or Perossa, variants of the affectionate diminutive Petruzza or Peruzza, feminine of Petro or Pero (Pietro). He considers unlikely a derivation from the various Perosa place names of Piedmont or a relation with the archaic name of Perugia.