The New Testament is a Christian book but the name Christian doesn’t appear in it much. Acts 11:26 says that “the disciples were first called Christians in Antioch,” a city in Syria.
The apostle Paul preached his faith before the Jewish ruler Agrippa, who referred to “[becoming] a Christian” (Acts 26:28). Enduring persecution as a Christian is mentioned in 1 Peter 4:16.
Much more common are the words brothers and believers, which have the same meaning as “fellow Christians.”