ANSWER: (1) "Christians." They were so called first by outsiders, then afterwards by themselves. Hence it is used only in Acts 11:26, 26:28 and I Pet. 4:16. (2) Disciples, answering to Master or Teacher. It was borrowed from the Jewish schools. Once, in Acts 19:1, those who had received only John's baptism are called disciples. (3) "Brethren." This was the first title given to Christians after the ascension (Acts 1:15, R. V.). It occurs twenty times afterwards in the same book. (4) The title "saints" (the holy) denoting the consecration and initial sanctification of believers. It is Paul's favorite term, being found thirty-one times in his epistles. John uses it only in the Revelation, and Jude only once.
— Steele's Answers pp. 251, 252.