It's interesting that Shimmun Keepa or Simon "the Rock," writes this letter as "Peter." I believe this was the age when many Jews started changing their names to foreign names. They typically picked common names to avoid persecution as Christians and later as Jews because of anti-Semitism.
In the early verses of Chapter Two, Peter explains the meaning and significance of his nickname "The Rock," (or as it is in English "Peter" from the Greek word for "rock,") and he compares it to the concept of "The Cornerstone," which refers to Jesus only. In Aramaic, "rock" and "stone" are designated by the same word. Peter clarifies for all time what the two concepts are all about.