The surname Quaglia has a mainly nickname origin, although in some cases it can also be considered toponymic. It derives from the Italian noun quaglia, which means "quail," and belongs to the group of zoological surnames formed from bynames associated with animals, whether for physical, behavioural or symbolic characteristics.

According to E. De Felice and F. De Laurentiis, the surname arises from a nickname already documented in the Middle Ages, with an early presence in Genoa in the year 1223, where the form Obertus Qualia Bergondius appears. Both authors agree that it is a cognominization typical of the medieval period, in which a byname based on an animal is progressively transformed into a hereditary surname.

Along the same lines, E. Rossoni notes that the surname may have a double origin. On the one hand, toponymic, linked to localities such as Quaglietta (Avellino), Quagliuzzo (Turin) or Quaglia di Berzo; and on the other, of a nickname nature, derived from the word quaglia, possibly related to the hunting or breeding of quails, or to symbolic traits attributed to the bird. Rossoni also documents its presence in northern Italy from the late Middle Ages, including records in regions such as Piedmont, Veneto, Friuli and Campania.

Among the variants and derived forms are Quaglino, Quaglini, Quagliana, Quagliato, Quaglio, Quagliarella, Quaglietta, Quagliariello, among others, the result of processes of suffixation, dialectal adaptation and family evolution of the original surname.

In sum, Quaglia is a surname of medieval origin, arisen from a nickname based on the name of a bird, with possible toponymic connections and a wide evolution of regional variants in northern and central Italy.