Letters to Cleo: St. Peter
Saint Peter, whose real name was actually Simon until Jesus renamed him, was one of the original Apostles, and considered to be chosen by Jesus himself as the first Pope. These days he's mostly known as the doorman at the Pearly Gates of heaven because of a line in the scripture about Jesus handing him the keys to heaven, thus he is often depicted holding a set of keys.
In scripture, Apostle Peter was considered the most devout, the most enthusiastic follower of Christ, and thus why he became heaven's proprietor. In the song, St. Peter is used for a bit of symbolism. The song is about someone who lies, who is not what he says he is. In the Bible, Jesus predicts that Peter will deny him three times in the course of a day, and in deed, he does deny his faith three times, despite being the most devout of all. But he also represents judgment of those who've sinned, a bit of a dichotomy, and both ways are expressed in the song. So, in this case, knowing a bit of history makes for a great song, despite it being a bit bitter considering it's name-dropping one of the Lord's close buddies.
And I can't believe I hadn't posted a Letters to Cleo song here yet. Perhaps this theme had some divine intervention?