Green’s Dictionary of Slang

to go back on one’s words, esp. to admit that a public statement was, in fact, wrong; one-off vars. include those at cits. 1923 and 1946.

[1607		Rowlands Diogenes Lanthorne 14: If he be not throughly frenchified, and well peper’d for his venerie, then I will for seauen yeares eate hay with a horse].
1772		Bridges Burlesque Homer (3rd edn) 15: I’ll eat my hat if you don’t scare him.
1836–7		Dickens Pickwick Papers (1999) 563: Well, if I knew as little of life as that, I’d eat my hat and swallow the buckle whole, said the clerical gentleman.
1838		Dickens Oliver Twist (1966) 370: A bad one! I’ll eat my hat if he is not a bad one.
1852		Stirling Obs. (Scot.) 19 Aug. 1/5: Let them carry the same load as I have to do [...] and if they didn’t get a sickener of the Kaffir war in that time, I’d eat my hat.
1865		Leaves from Diary of Celebrated Burglar 138/1: ‘I’ll eat my bloody ’at iv that ere’s anny ‘copper,’ ennywaiy,’ said Tom.
1876		C. Hindley Life and Adventures of a Cheap Jack 216: Set these needles in your land and in about four months [...] you’ll find them all grown into crowbars! or I’ll eat my hat, then swallow my boots.
1879		‘’Arry on the River’ Punch 9 Aug. 57/1: As for that younger gurl, Carry, / I’ll eat my old boots if she isn’t dead gone on Yours bloomingly, ’Arry.
1881		Dundee Courier 11 jan. 7/3: Weel, if that’s no a ‘sell’, I’ll eat my bonnet.
1887		E.E. Money Little Dutch Maiden II 148: And if you don’t run up against him next day in Bond Street you may eat your hat!
1889		L.A. Herald 18 Jan. 2/2: Come in and talk with my wife. If she can’t keep you busy I’ll eat my boots.
1892		E.J. Milliken ’Arry Ballads 38: If some of the swells didn’t ditto, I’ll eat my old hat, which it’s tough.
1902		Minneapolis Jrnl (MN) 5 May 2/2: If there’ eight ’undred Boers around there I’ll eat my boots.
1906		New Boys’ World 22 Dec. 84: By Jingo, the old woman is an old man, or I’ll eat my hat!
1907		Gem 16 Mar. 11: If this chap don’t go a full twenty, I’ll – I’ll eat my hat!
1910		O. Johnson Varmint 113: I’ll eat my pants!
1915		E. Pound letter 3 July in Read Letters to James Joyce (1968) 36: And if you aren’t worth ten De la Mares I’ll eat my shirt.
1918		Coconino Sun (Flagstaff, AZ) 8 Nov. 1/5: Oh boy, if it isn’t 110 in the shade I’ll eat my little white bonnet.
1918		R.D. Paine Fighting Fleets 143: This strange periscope, [...] – a Hun, or I’ll eat my hat.
1920		‘Sapper’ Bulldog Drummond 179: I’ll eat my hat if that Frenchman isn’t Franklyn [...] or any other of the blamed names he calls himself.
1923		Wodehouse Leave it to Psmith (1993) 571: And if it isn’t hidden somewheres in that McTodd’s shack down there in the woods I’ll eat my Sunday rubbers.
1929		J.B. Priestley Good Companions 436: Mark my words – if we’re not up, right at top o’t’tree, a’most afore you can say Jack Robi’son, I’ll eat this cap. [Ibid.] 605: An’ if he’s not proposin’ marritch the morn’s morn an’ if she’s no gladly acceptin’ him, ah’ll go an’ eat ma best bonnet.
1935		(con. 1920s) J.T. Farrell Judgement Day in Studs Lonigan (1936) 540: I’ll eat mine if I can’t drink you under the table.
1937		E. Garnett Family from One End Street 128: I’ll eat my hat if it ain’t that author with all the tins.
1938		D. Runyon ‘It Comes Up Mud’ Runyon on Broadway (1954) 546: If they are able to get him to the races again he will eat his old wool hat.
1946		J. Evans Halo in Blood (1988) 226: He called him out [...] and killed him. I’ll eat my 1928 deputy-sheriff’s star if he didn’t.
1956		I. Fleming Diamonds Are Forever (1958) 29: He’s not a diamond merchant, Sir [...] or I’ll eat my hat.
1959		A. Sinclair Breaking of Bumbo (1961) 66: Just show me once you are right, and the Brigade’s wrong, and I’ll eat my bloody bearskin.
1970		S. Naipaul Fireflies 325: Just look at that ring and if that is not a dollar sign I’ll eat my hat.
1982		M. Braun Judas Tree (1983) 109: I’ll eat your hat if he’s involved in these robberies.
2000		Indep. Rev. 15 Jan. 5: If that man doesn’t have the face of a leader of a Nazi death squad [...] I’ll eat my hat.
2007		S. Maloney Sucked In 119: If we can’t get a sausage roll here [...] I’ll eat my socks.