Green’s Dictionary of Slang

1. a peasant, a rustic and, as such, considered a fool or innocent; antonym of sharp n.¹ ; by extension any gullible individual irrespective of background; thus (UK Und.) it’s a good flat that’s never down, even the most naïve of dupes must realize what’s happening eventually.

1747		Life and Character of Moll King 12: I heard she made a Fam To-night, a Rum one, with Dainty Dasies, of a Flat from T’other Side.
1753		J. Poulter Discoveries (1774) 41: The Sharper has a quare Ned or Six ready to change, so keeps the good, and gives the bad one to the Flat.
1762		O. Goldsmith Life of Richard Nash in Coll. Works (1966) III 347: The two pickers up, or Money-Droppers, [...] bring in Flats or Bubbles.
1777		J. Fielding Thieving Detected 30: Oh no! says the Flat, I beg you’ll come in gentlemen.
1781–2		J. Messink Choice of Harlequin I viii: At your insurance office the flats you’ve taken in, / The game you’ve play’d, my kiddy, you’re always sure to win.
1791		Observer 4 Dec. 3: The proposal produced a universal laugh, but his Activity persisted in his bet, and was at length taken up by a Flat, who swore he knew better.
1809		J. Mackcoull Abuses of Justice 93: He was an excellent customer at hazard or backgammon. Perry said he had been told he was an excellent Flat, and often lost large sums of money.
1812		Vaux Vocab. of the Flash Lang. in McLachlan (1964) 241: flat: In a general sense, any honest man, or square cove, in opposition to a sharp or cross-cove; when used particularly, it means the person whom you have a design to rob or defraud, who is termed the flat, or the flatty-gory. A man who does any foolish or imprudent act, is called a flat; any person who is found an easy dupe to the designs of the family, is said to be a prime flat. It’s a good flat that’s never down, is a proverb among flash people; meaning, that though a man may be repeatedly duped or taken in, he must in the end have his eyes opened to his folly.
1821		‘An Amateur’ Real Life in London I 63: No man was better up to the rigs of the town; no one better down to the manoeuvres of the flats, and sharps.
1824		N.-Y. Eve. Post 23 Mar. 2/2: The mare had been beaten on a former occasion by the same horse, and anticipating the same result, the knowing ones bet 100 to 70 on the horse, which was readily taken up by the supposed flats.
1833		Ely’s Hawk and Buzzard (N.Y.) 21 Sept. 1/3: The nuns who were at the Bowery theatre on Monday night, found business on the increase, the flats bit well and some of the prime uns nibbled.
1833		‘Ye Scamps, Ye Pads, Ye Divers’ in Regular Thing, And No Mistake 62: At your Insurance Office the flats you’ve taken in; / The game you’ve play’d, my kiddy, you’re always sure to win.
1835		Sydney Herald 18 June 4/1: Lord how you does bamboozle them ere flats and swells.
1838		Paul Pry 20 Sept. 178/3: Some flats were found who posted the ready for him to fight the Poy Barney Aaron, perhaps under a belief that the Jew would make it right.
1841		Australasian Chron. (Sydney) 15 June 2/2: [W]hat a gulf there must be fixed between the gentlemanly flat and the genteel blackleg.
1845		J. Lindridge Sixteen-String Jack 129: Thinking they had got a flat, they induced me to play.
1852		Kendal Mercury 14 Feb. 3/3: The skipper and other members of the vagabond fraternity are ‘palavering the flats for balsam’ (humbugging the people for the coppers).
1853		N.Y. Times 28 Sept. 2: The Street-Boys [...] all have a slang language, so that they can recognize one another, and converse in a crowd. [...] To ‘tip a bust’ is to give a treat, and to ‘do a flat’ is to cheat a countryman.
1854		Delhi Sketch Bk 1 July 83/2: I know a trick worth two of that! / To spend my coin I’m no such flat!
1859		Bell’s Life in Sydney 23 Apr. 3/4: The pigeons were the last on the list [...] It did not require much skill [...] to tell that they were geuine flats.
1859		Matsell Vocabulum 15: Brush To flatter; to humbug [...] Brushing up a flat Praising or flattering.
1860		R. Nicholson Rogue’s Progress (1966) 71: There is not a word in the cant or flash vocabulary, nor indeed in the English language, taken in its right sense and meaning, that conveys so much, and is so generally applicable, as the simple monosyllable flat. There are flats of every rank, grade, and station in society, in every part of the known world, and, I dare day, in the unexplored portion also.
1867		Nat. Police Gaz. (NY) 21 Sept. n.p.: I ‘twigged’ them [i.e. a gang of pickpockets] ‘ramp’ a pair of opera-glasses from a ‘rep’ [...] She was under convoy of a ‘flat’.
1868		‘Do You Really Think She Did?’ in Rootle-Tum Songster 69: She could not live with such a flat, I was so very green!
1872		Galaxy (N.Y.) Apr. 494: A ‘flat gig’ is three numbers played for all three to be drawn, and gets its name, I presume, from the fact that it is played by nobody but fools, who are known in the dialect of detectives and thieves as ‘flats’.
1879		‘Autobiog. of a Thief’ in Macmillan’s Mag. (London) XL 502: The only thing that spurred (annoyed) me was me being such a flat to buy the home.
1880		Nat. Police Gaz. (NY) 4 Dec. 6/1: [headline] bowery green rooms / How the Sirens of those High-Toned Resorts ‘Bleed the Flats’.
1884		(con. 1730) A. Griffiths Chronicles of Newgate 208: Two iron rollers and two private springs, which those who were in the secret could touch and stop the turning [of the faro wheel] whenever they had flats to deal with.
1885		L. Emanuel Jottings [...] of a Bengal ‘qui hye’ 197: Of course, if Ràm-deen comes across a ‘flat’ or ‘griff’ as Johnny Newcome is called [...] victimizes him well and thoroughly.
1886		Eve. News (Sydney) 27 Apr. 7/4: I said ‘I am going for a bathe,’ and he took it, the flat, although if he had gone into Castlereagh-street he could have collared the cigars.
1890		Sporting Times 3 May 1/3: He utilised his winnings as groundbait for flats who were fly enough to kid themselves that they could clean him out and leave him granite-rocked at banker, shove-halfpenny, and penny nap.
1892		A.B. Paterson ‘Man from Ironbark’ in Bulletin 17 Dec. n.p.: I s’pose the flats is pretty green up there in Ironbark.
1894		J. Astley Fifty Years (2nd edn) I 170: I – like a real flat – decided that the abstemious habits of high training were no longer necessary.
1895		Harrington & LeBrunn [perf. Marie Lloyd] It’s a jolly fine game played slow 🎵 And he put an arm around my waist - so / I said, ‘I’m no flat! - after you with that’ .
1901		Boy’s Own Paper 12 Jan. 232: He wished now that old Holman had not been such a flat as to believe every word he had said.
1904		Sun. Times (Perth) 17 Jan. 12/3: I guessed they [i.e. two con-men] were lookin’ for ‘flats’.
1905		H.G. Wells Kipps (1952) 78: Flats who join touring companies under the impression that they are actors.
1910		Sun. Times (Perth) 30 Jan. 1st sect. 1/1: They Say [...] That while a susceptible flat as far as tarts are concerned he starves his own system.
1926		N. Fleischer in Ring Nov. 10: the flats--The suckers.
1928		T.W.H. Crosland ‘White Feather Legion’ in Last Poems 75: Then a health (we must drink it in whispers) / To the flats on the field and the foam, / And also to us, the pacific / Young Gentlemen Slackers at home.
1938		H. Asbury Sucker’s Progress 59: He had trimmed more ‘flats’ than any five of his contemporaries.
1971		L. Sanders Pleasures of Helen 137: ‘[Y]ou don’t really, honey, know what the hell it’s all about. What a flat you are! What a square!’.
1999		G. Seal Lingo 147: Other cheats were those who [...] organised catch-bets in which a decoy bet was made to entice a flat, or plunger (both fools and easy marks) to place a losing bet.

2. ext. of sense 1, a prostitute’s customer.

1790		‘Bowman Prigg’s Farewell’ in Wardroper (1995) 283: Then adieu to all kins and knots, / To kid-layers, files and trapanners, / To the buttocks and other fine flats / And all fellow men that have manners.
1841		‘Mother H’s Knocking Shop; or, A Bit Of Old Hat!’ in Gentleman’s Spicey Songster 45: By God, said the parson, you may think I’m a flat, / But I don’t mean to pray for the bit of old hat; / The old bawd hearing him, swearing said, ‘you’d best, / Or I’ll summons you up to the court of request’.
1858		G. Thompson Gay Girls of N.Y. 12: Our gay girl in white has ‘picked up a flat’ in the person of a rustic-looking individual from the country.
1869		J. Greenwood Seven Curses of London 318: Loose women are admitted [...] on the chance that she will, in the course of the evening, ‘pick up a flat’.

3. a bore, an unsophisticated individual.

1884		Sporting Times 29 Nov. 2/5: Araminta like James because he was ‘jolly;’ and she called John a ‘flat’ and that shocked her mother.
1890		Music Hall & Theatre Rev. 14 June 6/2: ‘our flat’ is having a good run at the Strand. We know several flats we should like to see doing the same—in fact, we should not grieve if they ran out of sight.

4. (also flatite, flattie) ext. as a common person, one who is not a member of an elite, i.e. a minor criminal.

1885		M. Davitt Leaves from a Prison Diary I 22: [It, i.e. successful] is what they invariably report themselves to be among ‘flats,’ i.e. the ignorant section of convicts who are outside the ‘profession.’.
1900		Bulletin (Sydney) 13 Jan. 24/3: It’s about time A.J.C. officials […] did a little towards providing a few conveniences for their ‘flat’ patrons. Every pony club lets its ‘flatite’ know the starters for each race […] but the superiah A.J.C. absolutely refuses to consider the beastly common person.
1921		(con. WWI) E. Lynch Somme Mud 246: You’ve heard of a man being called a flat, haven’t you, Sir?
2002		Observer Mag. 15 Sept. 8: The old showmen and women don’t like the independents like Ann and Phil. They call them ‘flatties’. They don’t belong.