Caesar

Originally the family name of Julias Caesar. The name was used, according to Roman custom, by those who had been adopted into his family, beginning with Octavian-Augustus. For reasons of prestige, however, Claudius, who succeeded Gaius-Caligula, decided to appended the name to himself even though he had no right to do so. His practice was followed by subsequent emperors. Eventually it became an imperial title implying the right as heir to the throne.

The word 'Caesar' morphed to become at a later time a title for European autocrats aspiring to imperial powers as the original Ceasars had, and, according to the different linguistic traditions, became Kaiser in German and Tsar or Csar in Russian.