According to the sources cited below, the surname may derive either from place names containing the root penna — widespread across Italy — or from nicknames of varied motivation.

E. De Felice notes that, as a toponymic base, Penna-type place names are particularly frequent in central and southern Italy: Penna in Teverina, in the province of Terni; Penna San Giovanni, in the province of Macerata; Penna Alta and Penna Sant'Andrea, in the province of Teramo; Pennadomo and Pennapiedimonte, in the province of Chieti; and Penne, in the province of Pescara. The demonyms derived from these localities may also have contributed to the surname's formation. As a nickname base, De Felice mentions forms derived from penna and its variants, or from pennello.

E. Rossoni adds that such nicknames could reflect the ancestor's occupation — for instance, that of a scribe. Rossoni also observes that penna carries the meaning of "peak" or "rock," which explains its frequent appearance in Italian place names, consistent with De Felice's toponymic observations. The third source likewise connects the surname to this dual origin: an occupational nickname for someone who worked as a writer, and the word penna in the sense of "peak" or "rock," as reflected in numerous place names.