Two observation must be made
on the Greek and the Latin
translations of Matthew
16:18.
Note in the Greek that the
name of Peter is Petros, and the
word for rock is petra.
In Latin the name of Peter is Petrus and
the word for rock is petra.
This follows from the
demands of the respective languages.
Nouns in these languages,
unlike English, have gender: some
are masculine (e.g., -os or
-us ending to words); some are
feminine (e.g., -a or -am
ending to words). The word for a rock
in both languages is, of its nature,
feminine; Peter, being a male,
could not take a feminine
ending to his name. It would be like
calling him "Rockette" instead of
"Rocky." Quite a difference!
Hence
it is only the demands of language that the gender
of the words is different.