In the study of Italian surnames it is essential to bear in mind the phenomenon of concurrence, that is, the possibility that one and the same surname may have more than one origin. This happens frequently as a result of linguistic evolution, dialect variants and the medieval habit of shortening or transforming given names.

A good example is provided by surnames such as Cullino, Ghelli, Ghezzi, Gucci, Guzzi, Guzzo, Ugolini, among many others, which may derive from a single root —such as the Germanic name Ugo (from hugu, "intelligence, wisdom")— but also from other, different names, or even from common words. From Ugo arose medieval forms such as Ugone, Ugolino, Uguccio, and from these, through processes such as aphaeresis (the loss of the initial syllable) and phonetic simplification, multiple variants were generated: Guccio, Gucci, Ghelli, Ghetti, Guzzi, and so on.

Not all of these surnames, however, necessarily share the same origin. Some, such as Gucci or Guccione, may derive either from Uguccio (related to Ugo) or from Arriguccio (a diminutive of Arrigo, that is, Henry). Others, such as Gussi or Guzzo, could have an entirely different origin, whether in medieval forms such as Gutius or even in words of everyday speech, such as guscio ("shell"), used as nicknames.

This crossing of possible origins shows that surnames do not always have a single, linear explanation. On the contrary, many of them are the result of parallel and convergent processes, in which different names, nicknames or words end up producing similar forms. Understanding concurrence therefore makes it possible to avoid simplistic readings and to recognize the richness and complexity of Italian onomastics.

As for the specific origin of the surname, E. Rossoni holds that it would descend from the medieval name Ghetius (Ghezzo), documented in Tortona in the second half of the 16th century. Its transformation into a surname is documented from the 17th century in the Siena area and in the Salentine area —that is, the southernmost zone of the region of Puglia, in the south of Italy—. A later addition notes that the surname would belong to old families native to the Como area and to the Brianza, and that the name probably alluded to the coat of arms, which depicted a lizard, called ghezz in dialect; the word ghezz also indicated in the past thin and slippery persons.