Basically equivalent to “Get out of my sight, Satan”, this insult seems pretty tame, until you realise that Jesus isn’t actually addressing Satan here. He’s addressing Peter, His disciple and one of His closest friends. And He calls him Satan. What?
Peter had an up-and-down kind of time following Jesus. In Matthew 16, we see a somewhat bizarre series of events. Jesus has just asked His disciples who the people are saying He is. The answers vary from John the Baptist (back from the dead) to Jeremiah (back from the dead) to Elijah (back from the sort-of-dead).
“But you,” Jesus presses further, “who do you say that I am?”
In what many people regard as an epiphany, Peter pipes up:
“You are the Messiah, the Son of the living God!”
“Correct!” says Jesus (more or less). He then goes on to explain that Peter is going to be the rock on which He builds His church. I imagine Peter was pretty chuffed.
But then Jesus starts telling his disciples what’s about to happen to Him. All that suffering, betrayal, and execution stuff, you know. Naturally, this is not what the disciples want or expect to hear, so Rocky takes Jesus aside and starts telling Him off:
“Nay Jesus, that ain't gonna happen to You. You’re completely wrong.”
Jesus turns to Peter, looks at him, and absolutely shuts him down:
“Get behind Me, Satan! You are an offence to Me because you’re not thinking about God’s concerns, but man’s.”
So in one conversation, Peter goes from the Rock of the Church to the Adversary of God. I’m almost impressed.
(After Jesus’ death and resurrection, Peter does indeed become an important figure in the early church.)
Peter’s name was actually Simon. But there are at least eight different Simons mentioned in the New Testament, including another of the twelve disciples, Simon the Zealot. So I guess nicknaming him Peter avoided some confusion.
The name Peter, or “Petros”, basically means “rock” in Greek (it’s the root of “petrify”). He’s also referred to as “Cephas”, which is the Aramaic equivalent.
Interestingly, the “Peter will be the rock on which I build My church” bit is where Catholics get the idea of the Pope. So yeah, according to the Catholic church, Peter was the first Pope.