The authors agree that the surname was formed from a medieval personal name of Germanic origin, whose second element is gaira/gairu ("spear"). Both recall that the surname was immortalised by Dante Alighieri (Florence, 1265 – Ravenna, 1321), author of the Divine Comedy.

E. Rossoni derives it from the medieval name Alighiero or Aldighiero, in turn from the Germanic Aldiger, composed of alda ("old") and gairu ("spear").

V. Blunda, for the Sicilian variant, derives it from the Germanic compound Alja Gaira ("another spear" or "second spear"), formed from alja ("other") and gaira ("spear"). He notes that Dante's Florentine family was of Lombard origin. He adds that the Sicilian form preserves the medieval Florentine spelling, testimony to the spread of the surname across the peninsula after the poet's literary fame.