1857. Ducange Anglicus, The Vulgar Tongue, p. 39. Fawney-droppers gammon the flats and take the yokels in.
1866. Yates, Black Sheep, I., p. 70. The genius which had hitherto been confined to bridging a pack of cards, or ‘securing’ a die, talking over a flat, or winning money of a greenhorn.
1880. Mortimer Collins, Thoughts in My Garden, vol. II., p. 180. Their quack medicines that will cure everything, and their sales of invaluable articles at a loss, and a thousand other devices to catch flats.
1887. W. E. Henley, Villon’s Good-night. You flats and joskins great and small.
1889. Pall Mall Gazette, Sept. 21, p. 3, col. 1 (In a London Gambling Hell). The flats who play faro (Cross-heading).
2. (American thieves’).—An honest man.
3. (American). A lover’s dismissal; a jilting.
Adj. (colloquial and literary).—Downright; plain; straightforward; as in that’s flat? a flat lie, “flat burglary,” etc.
1598. Shakspeare, 1 King Henry IV., Act I., Sc. 3. Wor.: You start away, And lend no ear to my purposes. Those prisoners you shall keep. Hot.: Nay, I will; that’s flat.
1835–40. Haliburton, The Clockmaker, p. 6, preface (ed. 1862).