E. De Felice and V. Blunda agree that the surname derives from the dialect term for 'parsley' and that it could have originated in a nickname linked to that plant.

E. De Felice notes that it was formed from old nicknames derived from prezzemolo, in its southern variants petrosino and petrosillo, the central petrosèllo, and the north-eastern parsìmolo, persòl and prasòl. The nicknames were given in relation to the aromatic plant or with the figurative sense of 'meddlesome, impertinent person'. He adds that the rare Sicilian surnames Petrosino may also derive from the place name Petrosino, in the province of Trapani.

V. Blunda, for the Sicilian variant, derives it from the word piddusìnu ('parsley'), which reflects the Byzantine Greek petrosélinon ('rock celery'), a loanword that entered Sicilian during the Byzantine domination. As a surname it could have originated in a nickname given to one who cultivated or traded the plant.