The authors agree that it is a surname of toponymic type, formed from the name of the Campanian city of Salerno. E. De Felice notes that it may also derive from the demonym salernitano, and that the variant Salierno predominates in the Naples area.

S. Vannozzi proposes two etymological hypotheses on the place name of origin. The first relates it to the Greek saos and the Latin salum ("sea," "open sea"), combined with the Etruscan-Campanian suffix -irno, modified by euphony into -erno. The second links it to the confluence of the rivers Sale (present-day Canalone) and Irno, between which the ancient settlement would have arisen. The related forms Salerni, Salernitano and Salierno share the same origin. Vannozzi documents the surname from the medieval period.