Dio’s praenomen is unknown, but he had still another cognomen, Cocceianus, which he derived along with the Dio from his maternal grandfather.  The latter, known as Dio of Prusa from his birthplace in Bithynia, is renowned for his speeches, which contain perhaps more philosophy than oratory and won for him from posterity the title of Chrysostom,—­“Golden Mouth.”  Dio of Prusa was exiled by the tyrant Domitian, but recalled and showered with favors by the emperor Cocceius Nerva (96-98 A.D.); from this patron he took the cognomen mentioned, Cocceianus, which he handed down to his illustrious grandson.

Besides this distinguished ancestor on his mother’s side Dio the historian had a father, Cassius Apronianus, of no mean importance.  He was a Roman senator and had been governor of Dalmatia and Cilicia; to the latter post Dio bore his father company (Books 49, 36; 69, 1; 72, 7).  The date of the historian’s birth is determined approximately as somewhere from 150 to 162 A.D., that is, during the last part of the reign of Antoninus Pius or at the beginning of the reign of Marcus Aurelius.  The town where he first saw the light was Nicaea in Bithynia.

The careful education which the youth must have had is evident, of course, in his work.  After the trip to Cilicia already referred to Dio came to Rome, probably not for the first time, arriving there early in the reign of Commodus (Book 72, 4).  This monster was overthrown in 192 A.D.; before his death Dio was a senator (Book 72, 16):  in other words, he was by that time above the minimum age, twenty-five years, required for admission to full senatorial standing; and thus we gain some scanty light respecting the date of his birth.  Under Commodus he had held no higher offices than those of quaestor and aedile:  Pertinax now, in the year 193, made him praetor (Book 73, 12).  Directly came the death of Pertinax, as likewise of his successor Julianus, and the accession of him whom Dio proudly hailed as the “Second Augustus,”—­Septimius Severus.  The new emperor exerted a great influence upon Dio’s political views.  He pretended that the gods had brought him forward, as they had Augustus, especially for his work.  The proofs of Heaven’s graciousness to this latest sovereign were probably by him delivered to Dio, who undertook to compile them into a little book and appears to have believed them all; Severus, indeed, had been remarkably successful at the outset.  Before long Dio had begun his great work, which he doubtless intended to bring to a triumphant conclusion amid the golden years of the new prince of peace.