|From an old book|
Q: Why did Jesus call himself a Nazarene to Paul in Acts 22:8? Who is a Nazarene?
A: Jesus came from Nazareth, a town so small and insignificant that it is never mentioned in the Old Testament and has left scant archaeological remains from the 1st century. John’s gospel indicates that it wasn’t held in high esteem.
While Jesus was still alive “Nazarene” was simply used as an identifier synonymous with the more familiar “…of Nazareth.” For instance, Mark — our earliest gospel — records this bit of conversation while Jesus was on trial: “seeing Peter warming himself, she looked at him and said, “You also were with the Nazarene, Jesus,” (Mark 14.67, ESV). The name Nazareth doesn't seem to have any connection to the Nazarites of the Old Testament and Jesus didn't follow the rites that identified one under a Nazarite vow, (see Numbers 6.1-21, ESV).
In Acts 22.8 Paul is in the land of Palestine, speaking to his fellow Jews in their native language. The Greek here is Ἰησοῦς ὁ Ναζωραῖος — literally, “Jesus, the one from Nazareth.” First century Jews didn’t use last names, so terms like “of this city” or “son of this man” were used to identify which person you were talking about. “Jesus” was actually a very common name back then, so all throughout the gospels and Acts “Jesus of Nazareth” is used to refer to the Jesus we are all familiar with. Here is a list of all the references to “Jesus of Nazareth” in the New Testament. There are actually more than that where “the prophet from Nazareth in Galilee” or some such is added.
After he died and rose again, the movement Jesus founded was known under various names, such as “Christians” and “the Way.” The Book of Acts indicates that another designation (probably used derisively, as “Christian” originally was) was “the Nazarenes:” “For we have found this man (Paul) a plague, one who stirs up riots among all the Jews throughout the world and is a ringleader of the sect of the Nazarenes,” (Acts 24.5, ESV).
So in his speech in Acts 22 Paul is most likely using “Jesus of Nazareth” just to identify what Jesus he is talking about. However, since he is speaking in the late AD 50s, when “the sect of the Nazarenes” was everywhere, he may have added that detail to connect the Jesus who met him on the road to Damascus with the founder of the despised Nazarene sect.