The successors of St. Peter are given authority by Christ in Hs Name to govern the Church on earth. Peter comes from the Greek word "Petros" meaning "Rock"; and Matthew 16:17-19 uses the term "Rock." Petros is the masculine version of the word "Petra," meaning "rock." It would, however, be incorrect to give a man a feminine name, thus the name Petros was given to him. In Hebrew/Aramaic it is the same, but with Kepha. Kepha means "rock." Christ would have originally called Simon "Kepha," since they spoke Aramaic as their first language. In the Gospel of St. John (specifically, ch. 21), Christ asked St. Peter 3 times "Do you love me," and Peter answered "yes" all 3 times, to which Christ responded: "Feed my sheep."
The scribe -- the sort of prime minister of old Israel -- was the one given the keys of the house of David in the Old Testament (Isaiah 22:22). The parallel to this in the New Testament is Christ giving the keys of heaven to St. Peter, the rock upon which Christ built His Church. (Matthew 16)