Medieval Latin biblia is short for biblia sacra "holy book", while biblia in Greek and Late Latin is neuter plural (gen. bibliorum). It gradually came to be regarded as a feminine singular noun (biblia, gen. bibliae) in medieval Latin, and so the word was loaned as a singular into the vernaculars of Western Europe. Latin biblia sacra "holy books" translates Greek biblia ta hagia, "the holy books".
