"the Scriptures of the Old and New Testaments," early 14c., from Anglo-Latin biblia, Old French bible (13c.) "the Bible," also any large book generally, from Medieval and Late Latin biblia "the Bible" (neuter plural interpreted as feminine singular), from phrase biblia sacra "holy books," a translation of Greek ta biblia to hagia "the holy books." The Latin word is from the Greek one, biblion "paper, scroll," also the ordinary word for "a book as a division of a larger work;" see biblio-.
The Christian scripture was referred to in Greek as Ta Biblia as early as c. 223. Bible replaced Old English biblioðece (see bibliothec) as the ordinary word for "the Scriptures." Figurative sense of "any authoritative book" is from 1804. Bible-thumper "strict Christian" is from 1870. Bible belt in reference to the swath of the U.S. South then dominated by fundamentalist Christians is from 1926; likely coined by H.L. Mencken in the "American Mercury."
Walter Scott and Pope's Homer were reading of my own election, but my mother forced me, by steady daily toil, to learn long chapters of the Bible by heart; as well as to read it every syllable through, aloud, hard names and all, from Genesis to the Apocalypse, about once a year; and to that discipline -- patient, accurate, and resolute -- I owe, not only a knowledge of the book, which I find occasionally serviceable, but much of my general power of taking pains, and the best part of my taste in literature. ... [O]nce knowing the 32nd of Deuteronomy, the 119th Psalm, the 15th of 1st Corinthians, the Sermon on the Mount, and most of the Apocalypse, every syllable by heart, and having always a way of thinking with myself what words meant, it was not possible for me, even in the foolishest times of youth, to write entirely superficial or formal English .... [John Ruskin, "Fors Clavigera," 1871]