 Many cognomina had unusual terminations for Latin names, ending in "-a, -o", or "-io", and their meanings were frequently obscure, even in antiquity; this seems to emphasize the manner in which many cognomina originally arose from nicknames.The "-ius" termination typical of Latin nomina was generally not used for cognomina until the fourth century AD, making it easier to distinguish between nomina and cognomina until the final centuries of the western empire.Unlike the nomen, which was passed down unchanged from father to son, cognomina could appear and disappear almost at will.