E. Rossoni notes that the surname derives from the Latin name Nanninus, documented in the Historia Francorum, and that its transformation into a surname is recorded in Florence in the 16th century, with the scholar Remigius Nanini of Florence serving as a concrete historical testimony. Rossoni considers the surname typical of Tuscany, with a presence also in the area of Bologna.

F. De Laurentiis proposes a different explanation for the base form: the starting point is Nanni, a hypocoristic of Giovanni. This given name derives from the ecclesiastical Latin Iohanne(m), which in turn adapts the Greek Ioánnes, itself a form of the Hebrew Yohanan, interpreted as "God had mercy" — where Yo- abbreviates Yahweh and hanán means "mercy." This derivation through Nanni is also consistent with the view recorded in Surnames in Italy, which identifies Nanni as a diminutive of the given name Giovanni as the basis of the surname.