Now it's accepted, it's been edited. Thank you for the comment ^.^ (Keep in mind thought that sometimes it's good to stick to word-to-word translations. Father is not wrong, but dad would be more precise no? ^.^)
It was about 1000 years ago, παπάς now only means "priest" because we call them "fathers" in Greece (!). When it took that meaning, παπάς as daddy was replaced by μπαμπάς with some foreign influence (I suppose to distinguish the meanings).