The authors agree that the surname was formed from the given name Alfonso, of Germanic origin, whose second element is funs/fus or funsa ("prompt, ready, prepared").

A. Bongioanni records as historical variants Adalfonso, Idelfonso and Ildefonso. He notes that the Germanic roots are athal or adal ("noble"), and funs or fus ("prompt" or "ready"). He recalls that the most venerated saint in Italy is Saint Alfonso de' Liguori, who died in 1787, celebrated on 2 August. He adds that in Italian surnames the Provençal form Anfós prevails.

V. Blunda, for the Sicilian variant, derives it from the Germanic compound Alla Funsa ("completely prepared" or "fully ready"), formed from alla ("all, whole") and funsa ("prepared, ready"), a root linked to warrior readiness.

Blunda stresses that it is a royal name par excellence in the Iberian Peninsula, and recalls that Alfonso X the Wise (1221–1284), king of Castile and León, was one of the great cultural patrons of the European Middle Ages. He notes that the surname spread in Sicily with Aragonese rule.