Green’s Dictionary of Slang

bibleback n.

1. a sanctimonious, ‘holier-than-thou’ person; thus a missionary or proselytizer.

[UK]Odd Fellow 24 Oct. 1/5: How expressive is the style of the sainted Malachi Bibleback! he stamps, he raves, he tears his hair, and his voice — alas! that voice.
[UK]Exeter Flying Post 2 July 5/3: These women had called her ‘Bible-back’ and other offensive names.
[UK]T.G. Vielé Following The Drum 162: The postmaster [... ] the only man in the settlement who owned a Bible, in consequence of which he had acquired the familiar cognomen of ‘Bible-back,’ a name that he stoutly resented!
Caldwell Tribune (ID) 16 Apr. 8/2: Old non-progressive Dilke calls me a ‘Canyon Brained Bible-back’.
[US]L.E. Ruggles Navy Explained 130: The navy generally calls a very religious person a bible pounder or bible back [HDAS].
[US]Colton & Randolph Rain II 128: You Bible backs don’t fool me. I’ve met you before!
[UK] in Partridge DU (1949) 35: [of religious prison workers] The ‘Bible-backs’ .
[US]Berrey & Van den Bark Amer. Thes. Sl.
[US]Monteleone Criminal Sl. (rev. edn).
[US]J. Blake Ex Post Facto in Joint (1972) 81: A Jew who had become a converted Baptist and posed as a Bible-toting evangelist. A type convicts called ‘Bible-Back’.
[UK]A. Sillitoe Sat. Night and Sun. Morning 173: What about them Bible-backs? They’re allus there wi’ their ha’ penny.
[US](con. 1950-1960) R.A. Freeman Dict. Inmate Sl. (Walla Walla, WA) 9: Bibleback – one who “gets” religion in stir to create an impression; generally a rapo or homo, etc.
[US] in PADS 42 35: More specific epithets [for Protestants] include bigoted Protestant [...] bible-back [...] and anti-Catholic.

2. attrib. use of sense 1, sanctimonious, pious.

[UK]Whitby Gaz. 16 Mar. 8/7: The ‘Bible-back’ state of religion [...] had passed.
[US]V.F. Nelson Prison Days and Nights 211: Take the chaplain [...] what does he know? Only what them goddam bibleback cons tell him.

3. fig. use of sense 1, a round-shouldered, hump-backed person.

[US]DN II 349: Bible-back [...] A round-shouldered, hump-backed person.

In derivatives

bible-backed (adj.) (US)

1. of a person, round-shouldered and hump-backed.

Olympia (Wash. Territory) Pioneer and Democrat 11 Dec. n.p.: We might in consequence [of poverty] become some what round-shouldered and ‘bible-backed’.
[UK]N&Q Ser. 4 XII 227: What kind of shoulders? Rather high. Anything else? He was humpy or bible-backed.
[US]Reno (NV) Weekly Gazette 24 Apr. 2/3: It is unfair for the newspapers in their reports of ministerial and other church trials to indulge in unsavory flings at prayer. The report usually says: [...] ‘Sister Biggs told Brother Hayne he was an old bible-backed, bug-eyed liar from Bitter creek,’ and winds up with ‘the doxology and benediction by Brother Myers’.
[UK]Brewer Dict. Phrase and Fable I 132/1: Bible-backed Round-shouldered, like one who is always poring over a book.
[US]M.G. Hayden ‘Terms Of Disparagement’ in DN IV:iii 217: bible-backed, round-shouldered.
[UK]Lincs. Echo 30 Jan. 1/1: In his view, the nation had become [...] ‘a nation of big-headed, bleary-eyed, Bible-backed lunatics’.

2. sanctimonious, oppressively pious; esp. of a Protestant who is conspicuously anti-Catholic.

[US]C. Panzram Journal of Murder in Gaddis & Long (2002) 241: Are there any Bible-backed cocksuckers in here? [...] I don’t need any Bible-backed hypocrites around me!
[US]Berrey & Van den Bark Amer. Thes. Sl.
[US] in DARE.
Quintessence of the Loon 🌐 This relates to ‘Americans For Purity: Winning The War On Masturbation’ mentioned on the Too Good to be True page. Perhaps the site owner wants to be promoted to full-strength loon. Nah! Nobody who really has a bible-backed right-wing-nut patriotic vigilante militia calls it that.