Hastings' Dictionary of the Bible (1898)
SER'GIUS PAU'LUS, the proconsul or deputy governor of Cyprus at the time of Paul and Barnabas' visit. He showed his intelligence and candor by sending for the apostles and accepting the overthrow of Elymas, the sorcerer, as demonstration of the overthrow of the creed Elymas represented. He embraced the gospel. Acts 13:7, Jud 4:12. Some think the apostle Paul took this name instead of Saul, in compliment to his distinguished convert: which is improbable.
It is a proof of Luke's minute accuracy that he calls Sergius Paulus a proconsul because the island had been governed by a propraetor during the reign of Augustus, but in the reign of Claudius, the time of the visit, as is proved by coins, it was under proconsular government.