The authors agree that this surname derives from the feminine given name Diana, coming from Roman mythology. E. De Stefani explains that Diana is considered a continuation of an earlier form, Diviana, derived from the Latin dia, feminine of dius, with the sense of "brilliant, luminous". She was the goddess of the moon and protectress of women, the feminine counterpart of Janus. Over time, the name became a surname.

Both authors note that in some Italian regions the name Diana also acquired the sense of "witch" by its association with a pagan divinity. De Stefani mentions this use in Friuli and in Sardinia, where it coexists with the variant Deiana, especially in the Sassari area. E. Rossoni adds that the origin of the surname in Sardinia could be of Ligurian root.

Rossoni incorporates a second etymological line: in some cases the surname could derive from place names, such as the Vallo di Diano in the Cilento. He also records formal variants: Diani, with presence in Lombardy, the Florence area and Lazio; and Diano, documented in the Naples area and in Calabria, particularly in the Reggio Calabria area. The surname Diana properly speaking appears in Campania, the Bari area and Sicily.