The gens Bellia, also written Billia and Bilia, was an obscure plebeian family at ancient Rome.
As the Bellii are not mentioned by ancient writers, there are no traditions relating to the origin of this gens, and the nomen is not listed among the gentilicia for which Chase was able to ascribe a particular origin; it resembles other gentiles formed using the suffixes -ilius, -ellius, and -illius, frequently derived from cognomina ending in -ulus, but sometimes from words ending in -illus or -ellus.
[1] The root was probably bellus, handsome or beautiful, but the use of surnames such as Clemens and Pacatus by some members of this gens suggests that the name was associated with bellum, war.
Primus, given in the filiation of a Roman matron from Gallia Narbonensis, was an archaic praenomen, but in its masculine form it was little used in historical times, except as a surname, or in Cisalpine Gaul, where unusual praenomina were fashionable.
Other surnames included Belliolus, a diminutive of Bellius, evidently given to a little boy; Clemens, gentle, mild; Marcellinus, a diminutive of Marcellus, probably indicating that an earlier ancestor was named Marcellus; Pacatus, peaceful, calm; Plautus, given to someone with broad or flat feet; and Reginus, indicating someone who came from Rhegium.