Holy Bible, according to the Online Etymology Dictionary, the word bible is from Latin biblia, traced from the same word through Medieval Latin and Late Latin, as used in the phrase biblia sacra (”holy book” - “In the Latin of the Middle Ages, the neuter plural for Biblia (gen. bibliorum) gradually came to be regarded as a feminine singular noun (biblia, gen. bibliae, in which singular form the word has passed into the languages of the Western world.”).
source: wiki
