The authors agree that the surname derives from the place name Trapani, a city on the western coast of Sicily. E. Rossoni and F. Miranda add the historical etymology: the name goes back to the Latin Drepanum and to the ancient Greek drépanon, meaning "sickle", in allusion to the shape of the peninsula on which the city sits.

Miranda also provides a detail of historical interest: Trapani figures among the surnames that the Sicilian Jews, forced to convert to Christianity, adopted after the Edict of expulsion of 1492, taking as a reference the place name of the locality where they resided.

E. De Felice notes that the surname was also formed from the demonym Trapanese and, locally, Trapanotto. Both De Felice and Miranda agree that the surname is concentrated mainly in Sicily, with a relevant presence also in Campania and Calabria; Miranda extends this distribution to Apulia and to the rest of Italy, where it appears in a scattered way.