I find it rather irritating that Tacitus, in his Annals, often refers to Germanicus as "Caesar," and with not much consistency.
And Tiberius as well, as I see now:
63. Maroboduus, now utterly deserted, had no resource but in the mercy of Caesar. Having crossed the Danube where it flows by the province of Noricum, he wrote to Tiberius, not like a fugitive or a suppliant, but as one who remembered his past greatness. When as a most famous king in former days he received invitations from many nations, he had still, he said, preferred the friendship of Rome. Caesar replied that he should have a safe and honourable home in Italy, if he would remain there, or, if his interests required something different, he might leave it under the same protection under which he had come.