According to E. De Felice, Aquino is a toponymic surname derived from the town of Aquino, located in the province of Frosinone, in southern Lazio. The surname originally identified individuals who came from or were associated with this locality and later became widespread throughout southern Lazio and much of southern Italy.

E. Rossoni agrees that the surname is closely linked to the place name Aquino, but also notes a possible connection with the Latin personal name Aquinus, documented in the writings of the Roman historian Tacitus. Nevertheless, he likewise considers the place name Aquino to be the most likely source of the surname.

The town of Aquino is historically famous as the birthplace of Thomas Aquinas, one of the most influential theologians and philosophers of the Middle Ages. The place name itself is generally associated with the Latin root aqua (“water”), reflecting the area's ancient geographical features.

Overall, Aquino is primarily a surname of geographical origin derived from the town of Aquino in Lazio, preserving the ancestral connection of the family to that historic locality.