The authors agree that the surname was formed from a nickname derived from the dialectal term arillo or arìddu ("cricket").

E. De Felice specifies that it has as its base a nickname and later personal name formed from the Neapolitan and southern arillo ("cricket"). He notes that Agrillo is the Italianised form, and that Agrillòtta —common especially in Reggio Calabria— is a derivative with the Calabrian and Sicilian suffix -òtta. He adds that the surname is widespread from the area of Naples —where Arillo is specific— to Calabria and eastern Sicily.

V. Blunda, for the Sicilian variant, derives it from the dialectal word arìddu ("cricket"), formed from a zoonymic nickname. He notes that nicknames based on this insect were common in Italian popular onomastics and usually alluded to restless, talkative or short-statured people. He adds that the variant Grillo, without the prosthetic a- characteristic of Sicilian, is the common form in standard Italian and spread throughout the peninsula.