Cassius Dio Cocceianus, Dio's Rome, Volume 4
“ Gaius was in the habit of nicknaming him "sissy" (though he was the hardiest of men) and whenever it came the turn of Chairea to command would give him some such watchword as "yearning" or "Venus." Again, an oracle had a short time before warned Gaius to beware of Cassius. The former, supposing that it had reference to Gaius Cassius, governor of Asia at the time, because he was a descendant of that Cassius who had slain Cæsar, had him brought as a prisoner. The person whose future conduct the divinity was really indicating to the emperor, however, was this Cassius Chairea. ”
