The authors agree that the surname may derive from the place name Assoro, a locality in the Enna area. F. Miranda specifies that this town received in Antiquity the Latin forms Assorus, Aseros, Asseros and Assoros, and that some link it to Assaracus, the mythical Trojan king, great-grandfather of Aeneas. Both Miranda and E. Rossoni also note a possible Arabic root in the terms azar or assar; Miranda also adds the Arabic zahr, with the senses of "flower", "chance" and "harm".

V. Blunda proposes a different etymology: he considers the surname a Sicilian dialectal phytonym derived from the word ásaru, which designates a plant with a creeping stem. According to Blunda, it may have arisen as a toponymic surname applied to those who lived near places where that herb abounded, or as a nickname, in parallel with other Sicilian surnames of plant base such as Allia, Arigano or Aruta. Miranda agrees in mentioning the ásaro as a toxic plant peculiar to arid environments.

As for its distribution, Rossoni locates it mainly in the Trapani area, especially Mazara del Vallo, while its variant Asero is concentrated in the Catania area. Miranda broadens the picture: the surname is typical of the Trapani area and extends throughout Sicily, with presence in the areas of Agrigento, Palermo, Enna, Caltanissetta and Catania, as well as specific areas of Lombardy, Emilia-Romagna, Lazio, Puglia and Tuscany.