Green’s Dictionary of Slang

swear v.

SE in slang uses

In phrases

swear blind (v.) [blind adv.1 ]

to affirm emphatically and without qualification.

[UK]J. Curtis They Drive by Night 154: Have a drink first, they’d be bound to hold him for hours questioning. No, if he had a wet they were stone ginger to smell it and swear blind he was drunk and that he’d killed her in a fight.
[UK]A. Sillitoe ‘The Disgrace of Jim Scarfedale’ Loneliness of the Long-Distance Runner (1960) 131: All his worries were over, he’d swear blind they were.
[UK]Indep. 19 July 19: The banks swear blind that they are, or soon will be, Year 2000 compliant.
swear by (v.)

to accept as the truth, to have complete faith in.

C. Lucas Essay on Waters Pt 3 138: [They] prescribe them to all patients, in what distemper soever, promiscuously; in some quantity, though it be but enough to swear by.
[Aus]Bulletin (Sydney) 9 May 22/1: The Town Clerk couldn’t stand us at any price; and yet all we had ever done to offend him was to canvass for fifteen solid days when the billet was vacant, in order to obtain the position for our girl’s brother, a promising young woolsorter, with more than enough education to swear by.
[Aus]Bulletin (Sydney) 19 Dec. 22/3: I hear she has tried to lure Slap. from these parts, but he swears by Australian sunshine, and refuses to budge.
swear off (v.) (also swear off on) [? one’s oath of self-denial]

to give up, to abandon, to renounce.

[US]‘Dan de Quille’ Big Bonanza (1947) 102: When he recovered he ‘swore off’ drinking.
[US]C.F. Lummis letter 18 Nov. in Byrkit Letters from the Southwest (1989) 97: He had taken in two strangers [...] who tried to rob him, and he had ‘swore off’ on all such hospitality.
[Aus]Bulletin (Sydney) 14 Sept. 13/2: Victoria is afflicted just now with an epidemic of teetotal mayors. Ballarat, Bendigo and half-a-dozen other places possess mayors who have ‘sworn off,’ and whose little corner cupboards are bare of whisky.
[US]Ade Forty Modern Fables 160: He said he was going to swear off on making his Room a Hang-Out for Sharks.
[US]A. Bierce letter 5 Jan. in Pope Letters of Ambrose Bierce (1922) 183: As to pot-steaks, toddies, and the like, I shall simply swear off eating and drinking.
[UK]P. Marks Plastic Age 231: You told me last week that you had sworn off poker. How come you’re playing again so soon?
[US]H. Miller Tropic of Capricorn (1964) 142: There had been others in the family who swore off, who went on the water wagon, as they used to say.
[Aus]D. Stivens Courtship of Uncle Henry 168: Metho Bill, the town’s fulltime drunk, swore off the drink and went on the waggon to make sure he would be sober for the match.
swear on a stack of Bibles (a mile high) (v.) (also swear on a stack of Bibles as high as one’s head, ...on a truckload of Bibles, ...on a bag of boomerangs)

(orig. US) to make an elaborate or exaggerated oath, usu. in the face of another’s disbelief.

[US] DN III 378: Swear on a stack of Bibles (a mile high), [...] an exaggerated or emphatic form of oath.
[UK]R.D. Paine Fighting Fleets 368: The chief gunner honestly believes he hit and disabled her and will swear to it on a stack of Bibles as high as the mainmast.
[US] in J.F. Dobie Rainbow in Morning (1965) 82: I would not believe him if he swore to it on a stack of Bibles as high as his head.
[US](con. late 19C) E. Cunningham Triggernometry (1957) 375: We’ll go out and borrow a Bible – two Bibles – a dozen Bibles! And I’ll swear on all that stack.
[US]E. O’Neill Long Day’s Journey into Night II ii: I wouldn’t believe him if he swore on a stack of Bibles.
[UK]E. Hill Territory 446: In the bush you ‘swear on a bag of boomerangs’.
[US]Billie Holiday Lady Sings the Blues (1973) 24: Mom [...] swore on a stack of Bibles I was eighteen.
[US]‘Tom Pendleton’ Iron Orchard (1967) 183: I’d take a paralyzed oath to it on a forty-foot stack a’ Bibles!
[US](con. 1998–2000) J. Lerner You Got Nothing Coming 73: Swearing on one’s white skin is sacred to Kansas. Carried more credibility than swearing on a truckload of Bibles.
swear to beef

(US black) a general interrogatory phr.

[US]Ebonics Primer at [Internet] swerta beef Definition: ‘For Real?’ ‘Is that the truth?’ Example: Swerta beef that happened yesterday?