This bit was mentioned under the heading of puns in M. H. Abrams’ A Glossary of Literary Terms .
Thou art Peter [Petros] and upon this rock [petra] I will build my church.
I never really noticed it before, but it is definitely there. It makes me wonder what other sorts of punnery there is in the New Testament. I wonder if someone has done a study of the uses of puns in the Bible and their significance.