E. Rossoni considers that the surname derives, directly or through diminutive forms, from the medieval name Diamante, used both as masculine and feminine. He documents this form in a deed of 1571 in Milan. The variants Diamante, Diamanti and Diamantini present differentiated geographical distributions: the first is recorded in the Udine area, Genoa, Rome, the Frosinone area, the Potenza area, Puglia and the Syracuse area; the second appears in the Massa area, the area between Bologna and Modena, the Ancona area, the Macerata area, the Ascoli Piceno area, the Perugia area, the Terni area, the Grosseto area, the Viterbo area, Rome, the Latina area and the Frosinone area; the third is located in the Rimini area, the Pesaro area, the Ancona area —particularly Senigallia—, the Perugia area —especially Gubbio— and Rome.

V. Blunda, on the other hand, proposes a different origin for the case of Sicily: the surname would come from the Greek adàmantos, a term that designates the hard and transparent precious stone. According to Blunda, it would have functioned as a nickname applied to an ancestor for his firmness of character, his valour or another trait associated with that material in the tradition, becoming over time a surname in Sicily.