There is no distinction the the Aramaic that our Lord spoke.
Pure speculation. Show me the Aramaic. Don't have it? Hmmmm.
Here's the deal. The exact language Jesus spoke in any given circumstance is unknown except for where the text directly identifies it. Given His close proximity to the multicultural nexus of Cesarea, it is possible He spoke in Greek, Latin, Hebrew AND Aramaic at various times and circumstances. Please take a look at this link for some current thinking on the matter:
http://www.hebrew4christians.com/Articles/Jesus_Hebrew/jesus_hebrew.html
So without an actual Aramaic text, no one knows of Jesus said this in Aramaic, Hebrew or Greek. Therefore, anyone confidently proclaiming they know with certainty that anything was said in Aramaic in Matthew 16:18 is talking through their hat. Sorry about that.
But even if for the sake of argument we grant the unprovable assumption this was said in Aramaic, there is still good reason to accept a distinction in the two terms. This is because even in Aramaic there were other terms for Rock than Kepha that may well have occupied the second slot, and there is evidence from the Syriac that this is
exactly how those early translators perceived the situation, using,
not Kepha, but
Tnra (another Aramaic word for stone) in the second slot, to preserve the distinction. Two. Different. Words.
As for what Jesus actually said, the RC hypothesis that the two terms in Greek are different solely due to gender alignment is false. According to recent scholarship, Petros was already serviceable as a proper name, meaning it was NOT a gender-adjusted form of Petra to avoid a feminine effect. The name in it's own right already conformed to the masculine pattern.
Furthermore, the fact that Petros shares a root with Petra is not enough to demonstrate they are the same word. Many distinguishable words share common roots. If I said, "You are Rocky, and on this Rock I will build an indestructible spiritual family," are you really going to miss the distinction I'm making? No, of course not. The fact remains that if Jesus wanted to make sure we understood that it was Peter He spoke of in both places, Petros could have been used in both places: "You are Rocky, and on you, Rocky, I will build an indestructible spiritual family." That would have kept the second person form of address in tact.
But instead, Matthew introduces the demonstrative pronoun "this" (ταύτῃ), jarring the listener
out of the address to Peter, and signaling a new, 3rd person referent. This makes it clear, unmistakable, that Jesus is NOT making reference to the same person. Furthermore, it was very comon for Jesus to use theird person titles to refer to Himslef, "You will see the Son of Man sitting on the right hand of power, and coming in the clouds of heaven," etc.
On the other hand, if Matthew had in fact wanted to show they were the same person, He could easily have used Petra for Peter in the first slot AND the second, because contrary to what you may have heard, some masculine Greek names
do have the feminine ending. Example you say? Sure. Zorba the Greek. Feminine ending on a masculine name. Go figure. So if the alleged underlying Aramaic was really Kepha/Kepha, that could be rendered with equally symmetry into the Greek (Petra/Petra) without fussing about gender endings.
Bottom line? Those two Greek words bolded below really are
two different words, not the same word adjusted for gender setting:
Matthew 16:18 Κἀγὼ δέ σοι λέγω, ὅτι σὺ εἶ Πέτρος, καὶ ἐπὶ ταύτῃ τῇ πέτρᾳ οἰκοδομήσω μου τὴν ἐκκλησίαν, καὶ πύλαι ᾍδου οὐ κατισχύσουσιν αὐτῆς.
If you or anyone else is interested to some serious scholarship on the matter, I would direct your attention to a book called Peter and the Rock, by Chrys C. Caragounis, which is a very detailed analysis of the linguistic possibilities in Matthew 16:18, including an excellent survey of the multiple Aramaic terms that could have been used behind Petra. It is expensive, but well worth it.
Peace,
SR