Opsidia gens
The gens Opsidia or Obsidia was an obscure plebeian family at ancient Rome. Few members of this gens are known to have held any magistracies, but several are found in inscriptions. One Obsidius gave his name to the volcanic glass obsidian. Origin. The nomen "Opsidius" belongs to a class of gentilicia formed from other names using the suffix "-idius". In this case the nomen is derived from the more common "Opsius"; the same nomen also gives rise to the gens Opsilia. The common root of all three nomina is "op-", "help", found in the name of the goddess  Ops, as well as the praenomen "Opiter", and the derived patronymics "Opiternius" and "Opetreius", and the nomen "Oppius". Most of these names are thought to be of Sabine or Samnite origin, and in some writers we find the nomen "Obsidius", apparently an orthographic variation of "Opsidius", among the Frentani, a Samnite people. At a later period, a Roman traveler of this name is said to have discovered the type of volcanic rock now known as obsidian, which became highly fashionable at Rome.