Hail Caesar: The evolution of family name to imperial title

"The princes who by their birth or their adoption belonged to the family of the Caesars, took the name of Caesar.    After the death of Nero, this name designated the Imperial dignity itself, and afterwards the appointed successor. - Footnote, Gibbon's Decline and Fall of the Roman Empire

However, scholars in Gibbon's time were unsure of the exact point in the Roman succession that the name transitioned to an imperial title.

Augustus as Pontifex Maximus

photographed at the Palazzo

Massimo in Rome by Mary

Harrsch.

"The time at which it was employed in the latter sense, cannot be fixed with certainty. Bach (Hist. Jurisprud. Rom. 304) affirms from Tacitus, H. i. 15, and Suetonius, Galba, 17, that Galba conferred on Piso Lucinianus the title of Caesar, and from that time the term had this meaning: but these two historians simply say that he appointed Piso his successor, and do not mention the word Caesar.  [Actually, Galba himself assumed the title "Servius Galba Imperator Caesar" then passed it on by adoption to his successor.]

Aurelius Victor (in Traj. 348, ed. Artzen) says that Hadrian first received this title on his adoption; but as the adoption of Hadrian is still doubtful, and besides this, as Trajan, on his death-bed, was not likely to have created a new title for his successor, it is more probable that Aelius Verus was the first who was called Caesar when adopted by Hadrian. Spart. in Aelio Vero, 102.- W."   - Footnote, Gibbon's Decline and Fall of the Roman Empire

Adoption certainly accounts for Augustus, who was adopted by Julius Caesar, and Tiberius, who was subsequently adopted by Augustus.  Claudius assumed the name of Caesar upon accession without previous adoption but he was a direct descendant of Caesar's bloodline.  Claudius later adopted Lucius Domitius Ahenobarbus (Nero) thus transmitting the name Caesar to him. So Gibbon's initial observations are correct.  However,  Gibbon seems to become a bit confused with the successions occurring in the Year of the Four Emperors.

Roman emperor Otho in 69 CE.  
Photographed at The Louvre in Paris
by Mary Harrsch.

"Galba's reign did not last long and he was soon deposed by Marcus Otho. Otho did not use the title "Caesar", but occasionally used the title "Nero" as emperor. Otho was then defeated by Aulus Vitellius who acceded with the name "Aulus Vitellius Germanicus Imperator Augustus." Vitellius did not at first adopt the cognomen "Caesar" as part of his name, and may have intended to replace it with "Germanicus" (he bestowed the name "Germanicus" upon his own son that year).

Publis Septimus Geta 3rd century CE.

Photographed at the Palazzo Altemps

in Rome by Mary Harrsch.

Nevertheless, Caesar had become such an integral part of the imperial dignity that its place was immediately restored by Titus Flavius Vespasianus ("Vespasian"), whose defeat of Vitellius in 69 [CE] put an end to the period of instability and began the Flavian dynasty. Vespasian's son, Titus Flavius Vespasianus became "Titus Caesar Vespasianus". - Wikipedia

Following the Flavians, the emperor Nerva assumed the title as well then passed it on through adoption to his heir  Caesar Nerva Traianus who, supposedly, adopted his heir Hadrian, passing the title to him.  At this point our path once more converges with Gibbon.


I thought it was also interesting to read that to further distinguish the use of the name to designate the imperial heir, the title Nobilissimus (meaning "most noble") was added in the 3rd century CE beginning with  Publius Septimius Geta.