Again, from the above post:
Note that Christ did not speak to the disciples in Greek. He spoke Aramaic, the common language of Palestine at that time. In that language the word for rock is kepha, which is what Jesus called him in everyday speech (note that in John 1:42 he was told, "You will be called Cephas"). What Jesus said in Matthew 16:18 was: "You are Kepha, and upon this kepha I will build my Church."
When Matthews Gospel was translated from the original Aramaic to Greek, there arose a problem which did not confront the evangelist when he first composed his account of Christs life. In Aramaic the word kepha has the same ending whether it refers to a rock or is used as a mans name. In Greek, though, the word for rock, petra, is feminine in gender. The translator could use it for the second appearance of kepha in the sentence, but not for the first because it would be inappropriate to give a man a feminine name. So he put a masculine ending on it, and hence Peter became Petros.
Please provide a link to the facsimile of the Aramaic text of Matthew.
I won't hold my breath waiting ...