Why would "
Maria" have to have been used before
Mary had a baby?
Maria is a Latin form of
Miriam or
Mariam, and was originally a mistake by those who translated the Bible from Greek into Latin and assumed the -m was just an accusative case ending instead of being an integral part of the original Hebrew name. So
Maria may well not have existed as a form of the name until the New Testament was translated into Latin, and so does not have to have existed as a name before
Jesus was born.