"Petras" is rock, feminine noun.
"Petros" is masculine form corresponding to "Petras". Simon could not be called "Petras" because he is a man; no other gradation of meaning is in the text.
God giving a new name to someone is a sign of spiritual regeneration when an important historical role is given. It is used throughout the Bible, witness Abram - Abraham, Jacob - Israel.
Thanks again. I wish I had my concordance here. My rule of thumb is that English is pretty much all I need because the single most important rule of interpretation is "Let Scripture interpret scripture". Since there is no other scripture telling us about Peter's popehood, I don't see a popehood. Otherwise, we could have made a big thing out of "sons of thunder".
"Use the [Internet], Luke."
Chances are, the concordance you want is online. If this isn't it, Google the one you want. ;)
The commission of Peter is self-explanatory in his relation to the Church, -- he is given a new name and called the foundation of the Church. It would be extra-scriptural to assume some other meaning in that verse. In Acts, it is rather clear that while others disagree with him, Peter is the one giving the final approval to the doctrine they jointly developed. This is functionally papacy, although the degree of authority the the Pope has among the bishops is matter of debate and interpretation, and it changed through the ages.
When John is named Son of Thunder, there is no particular reason given in the scripture, this is why we don't speculate on any ecclesiastical role of John.
In Mt 16:18 and Jn 1:42 Simon Peter is renamed Rock and in Mt 16:18 te reason for the name is given, to become the foundation of Christ's Church.
In Mt 16:10 Peter alone is given the keys with which to bind and loose things on earth. Christ promises that what Peter legislates on earth will be followed in heaven.
In Jn 21:15-18 Peter alone receives the pastoral duty to feed and guide Christ's sheep.