I think you will want to start reading here -
catholic-pages.com/pope/hahn.asp
In addittion, we know Jesus spoke Aramaic because of what others have already said - He spoke it on the cross and he spoke it when he healed the girl. In addition some of the text you can tell was translated from Aramaic to Greek.
Now for the clincher. Saying that Petros means little pebble and Petra means large rock shows a faulty knowledge of first century Koine Greek. I will quote an excerpt from a Catholic Answers article to show this.
"As Greek scholars—even non-Catholic ones—admit, the words petros and petra were synonyms in first century Greek. They meant “small stone” and “large rock” in some ancient Greek poetry, centuries before the time of Christ, but that distinction had disappeared from the language by the time Matthew’s Gospel was rendered in Greek. The difference in meaning can only be found in Attic Greek, but the New Testament was written in Koine Greek—an entirely different dialect. In Koine Greek, both petros andpetra simply meant “rock.” If Jesus had wanted to call Simon a small stone, the Greek lithos would have been used. The missionary’s argument didn’t work and showed a faulty knowledge of Greek.
(For an Evangelical Protestant Greek scholar’s admission of this, see D. A. Carson, The Expositor’s Bible Commentary [Grand Rapids: Zondervan, 1984], Frank E. Gaebelein, ed., 8:368)."
catholic.com/tracts/peter-the-rock
Finally, just examining the context of the text yields the result that Peter is the rock. Even Protestant scholars agree on this. Any attempt to circumvent this is done because of the opposition to Catholic interpretation and its implication and has nothing to do with what the text actually means to an objective observer. At the very base level the question should be at least why is Peter the only apostle or person in the bible to have his name changed to rock? That has to mean something! Protestants can not just write that off as meaningless!
"Blessed are YOU, Simon Bar-Jona!.. And I tell YOU, YOU are Peter [which means rock], and on this rock I will build my church… I will give YOU the keys of the kingdom of heaven, and whatever YOU bind on earth shall be bound in heaven, and whatever YOU loose on earth shall be loosed in heaven.”
Here Jesus calls Simon blessed! Then he calls him rock and says upon this rock he will build his church. And then he blesses him again by saying he will give him the keys of the kingdom and he will have authority in heaven and on earth. So we see really Peter is being blessed 3 times by Jesus. It would make no sense for Jesus to bless Peter and then call him a little pebble to make light of him, but still give Peter the keys to the kingdom and authority in heaven and earth. The context of the passage is a blessing to Peter. And as we see Jesus uses the language of Is 22 where we see the changing of the Prime Minister of the Davidic Kingdom. Since Jesus is the new Davidic King whose thrown will never end, it is entirely his right to appoint his Prime Minister to be Peter.
“In that day I will call my servant Eliakim the son of Hilkiah, and I will clothe him with your robe, and will bind your girdle on him, and will commit your authority to his hand; and he shall be a father to the inhabitants of Jerusalem and to the house of Judah. And I will place on his shoulder the key of the house of David; he shall open, and none shall shut; and he shall shut, and none shall open. And I will fasten him like a peg in a sure place, and he will become a throne of honor to his father’s house.”
Many Protestant scholars admit that Peter is the rock, however they get around this by denying that Peter’s office was succeeded or by saying that Mt 16:15-19 was a later addition to the text and not part of the original. However, the office of Prime Minister denotes succession. Prime Minister’s were replaced and succeeded by new one’s in the Davidic Kingdom as can be seen in Is 22:15+. And, if you want to start throwing out texts from the bible that you don’t agree with that is a slippery slope.
