Acts 25:21

But when Paul had appealed to be reserved
In custody at Caesarea:

unto the hearing of Augustus;
to have his cause heard, tried, and judged of, by the Roman Emperor Nero, here called Augustus; for as it was usual for a Roman emperor to be called Caesar, from Julius Caesar, the first of them, so to be called Augustus, from Octavius Augustus, the second emperor: his original surname was Thurinus, but this being objected to him as a reproachful one, he afterwards took the name of Caesar, and then of Augustus; the one by the will of his great uncle, the other by the advice of Munatius Plancus; when some thought he ought to be called Romulus, as if he was the founder of the city, it prevailed that he should rather be called Augustus; not only this surname being new, but more grand, seeing religious places, and in which anything was consecrated by soothsaying, were called "Augusta, ab auctu, vel ab avium gestu, gustuve", according to Ennius ^F20: in the Greek text the name is Sebastos, which signifies venerable and worshipful.

I commanded him to be kept;
in Caesarea, by a centurion, and not sent to Jerusalem:

till I might send him to Caesar:
till he could have an opportunity of sending him to Rome, to take his trial before the emperor.