Host Martin Tanner describes how Papias in 140 AD said "Mark . . . the interpreter of Peter, wrote accurately but not in order all" Peter told him about the life of Jesus. Luke's Gospel says he "wrote in order" meaning he corrected the order.  Luke also supplemented Mark's Gospel with additional information from "eyewitnesses" at a time when there were many accounts of the life of Jesus.  The earliest Christians called their religion the "New Covenant" or sometimes "The Way" of Jesus or as taught by Jesus.  "Christians" was a put down by outsiders, which over time became the new way the early Church was described.