Christianity began in the 1st century AD as a Jewish sect but quickly spread throughout the Greco-Roman world.
The word revelation never occurs again in the book that has come to bear that name. Every other time the book refers to itself, it is as a prophecy (v. 3; compare 22:7, 10, 18) or a "book of prophecy" (22:19). Revelation should therefore be understood in much the same sense as in 1 Corinthians 14:6, 26, where Paul lists "a revelation" among the things prophets in early Christian congregations received from God in the Spirit--along with knowledge, prophecy, teaching (v. 6), a psalm, a teaching, a tongue, an interpretation (v. 26).
Paul uses the phrase "revelation of Jesus Christ" in Galatians 1:12 (NRSV) to refer to the divine message he had received, and by virtue of which he became apostle to the Gentiles. Both in Galatians and here in Revelation the phrase "revelation of Jesus Christ" tells us primarily where the revelation comes from, not what it is about. It is a revelation given by Jesus Christ from heaven, now that God has raised him from the dead. Much of it, of course, will also be about Jesus, but above all the title is saying that the book is from Jesus. ©InterVarsity Press
12 For I did not receive it from any man, nor was I taught it, but I received it through a revelation of Jesus Christ. (Galatians 1:12 ESV)