Act_11:26 And when he [Barnabus] had found him [Saul], he brought him unto Antioch. And it came to pass, that a whole year they assembled themselves with the church, and taught much people. And the disciples [G3101] were called Christians [G5546] first in Antioch.
From G3129; a learner, that is, pupil: - disciple.
From G5547; a Christian, that is, follower of Christ: - Christian.
“And the disciples were called Christians first at Antioch - It is evident they had the name Christians from Christ their master; as the Platonists and Pythagoreans had their name from their masters, Plato and Pythagoras. Now, as these had their name from those great masters because they attended their teaching, and credited their doctrines, so the disciples were called Christians because they took Christ for their teacher, crediting his doctrines, and following the rule of life laid down by him. It has been a question, by whom was this name given to the disciples? Some think they assumed it; others, that the inhabitants of Antioch gave it to them; and others, that it was given by Saul and Barnabas. This later opinion is favored by the Codex Bezae, which reads the 25th and 26th verses thus: And hearing that Saul was at Tarsus, he departed, seeking for him; and having found him, he besought him to come to Antioch; who, when they were come, assembled with the Church a whole year, and instructed a great number; and there they first called the disciples at Antioch Christians.
The word χρηματισαι in our common text, which we translate were called, signifies in the New Testament, to appoint, warn, or nominate, by Divine direction. In this sense, the word is used, Mat_2:12; Luk_2:26; and in the preceding chapter of this book, Act_10:22. If, therefore, the name was given by Divine appointment, it as most likely that Saul and Barnabas were directed to give it; and that, therefore, the name Christian is from God, as well as that grace and holiness which are so essentially required and implied in the character.
Before this time. the Jewish converts were simply called, among themselves, disciples, i.e. scholars; believers, saints, the Church, or assembly; and, by their enemies, Nazarenes, Galileans, the men of this way or sect; and perhaps lay other names which are not come down to us. They considered themselves as one family; and hence the appellation of brethren was frequent among them.
It was the design of God to make all who believed of one heart and one soul, that they might consider him as their Father, and live and love like children of the same household. A Christian, therefore, is the highest character which any human being can bear upon earth; and to receive it from God, as those appear to have done - how glorious the title!” Adam Clarke
NOTE: We are living in the time of the great apostasy. Most of Christianity is no longer following the teaching of Christ; but there remains a faithful remnant who call themselves “Christian” who will suffer and die for their faith in the Father and His Son Jesus Christ. Let us learn to discern the body of Christ and not be ashamed of our calling:
1 Peter 4:16 Yet if any man suffer as a Christian, let him not be ashamed; but let him glorify God on this behalf.
To clarify - those who commit sin may call themselves "Christians" but they are NOT born of God. They remain children of the devil.
1 John 3:8 He that committeth sin is of the devil; for the devil sinneth from the beginning.
1 John 3:9 Whosoever is born of God doth not commit sin;
1 John 5:18 We know that whosoever is born of God sinneth not;
1 John 3:6 Whosoever abideth in him sinneth not: whosoever sinneth hath not seen him, neither known him.