similar pattern was followed by Augustus' heirs. The emperor's stepson and eventual successor was born Tiberius Claudius Nero; after his adoption by the emperor, he became Tiberius Julius Caesar (retaining his original praenomen). His brother, born Decimus Claudius Nero, subsequently became Nero Claudius Drusus, exchanging his original praenomen for his paternal cognomen, and assuming a new cognomen from his maternal grandfather. Other members of the Julio-Claudian dynasty used praenomina such as Drusus and Germanicus. In subsequent generations, all reigning emperors assumed Imperator as an additional praenomen (usually without foregoing their original praenomina), and Augustus as a cognomen. Caesar came to be used as a cognomen designating an heir apparent; and for the first two centuries of the empire, most emperors were adopted by their predecessors. The result was that each emperor bore a series of names that had more to do with the previous emperor than the names with which he had been born. They added new cognomina as they fought and conquered enemies and new lands, and their filiations recorded their descent from a series of gods. As the names of the emperors themselves changed, so did the names of the members of their families. Later development During the Empire, a variety of new naming conventions developed which, while differing, were internally coherent. Binary nomenclature and polyonymy Under the "High Empire", the new aristocracy began adopting two or more nomina – a practice which has been termed 'binary nomenclature'. This arose out of a desire to incorporate distinguished maternal ancestry in a name or, in order to inherit property, an heir was required by a will to incorporate the testator's name into his own name. For example, the suffect consul of AD 118/9, Gaius Bruttius Praesens Lucius Fulvius Rusticus, has a name which is composed of two standard sets of tria nomina: he was the natural son of a Lucius Bruttius, and added the nomina of his maternal grandfather, Lucius Fulvius Rusticus, to his paternal nomina. In order to reflect an illustrious pedigree or other connections, the aristocracy expanded the binary nomenclature concept to include other nomina from an individual's paternal and maternal ancestry. There was no limit to the number of names which could be added in this way (known as polyonomy), and, for example, the consul of 169 AD, (usually called Q. Sosius Priscus) had thirty-eight names comprising fourteen sets of nomina reflecting a complex pedigree stretching