Green’s Dictionary of Slang

1. a bedsheet.

c.1566		Harman Caveat for Common Cursetours in Viles & Furnivall (1907) 83: a slate or slates a shete or shetes.
1592		Groundworke of Conny-catching Ch. 16: Some of these [a demaunder for glimmar] go with slates at their backes, which is a sheete to lye in a nights.
1608		Dekker Belman of London D3: Kinching Morts [...] are girles of a yeare or two old, which the Morts (their mothers) carry at their backes in their Slates (which in the Canting tongue are sheetes).
1610		Rowlands Martin Mark-all 42: O Ben mort will thou pad with me / One ben slate shall serue both thee & me.
1622		Beaumont & Fletcher Beggar’s Bush III iv: To maund on the pad, and strike all the cheats, / To mill from the Ruffmans, Commission and slates.
1639		J. Taylor Crabtree Lectures 193: Mort. If you tower any states [sic] lye upon the Cracke, mill them, and budge a beak.
1648		Dekker Canters Dict. in Eng. Villainies (9th edn).
1665		Head Eng. Rogue I 52: Slate, a Sheet.
1674		Head Canting Academy (2nd edn) 63: [as cit. 1608].
1688		R. Holme Academy of Armory Ch. iii item 68c: Canting Terms used by Beggars, Vagabonds, Cheaters, Cripples and Bedlams. [...] Slate, a Sheet.
1707		J. Shirley Triumph of Wit 198: [as cit. 1637].
1754		Scoundrel’s Dict.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
a.1790		H.T. Potter New Dict. Cant (1795).
1809		G. Andrewes Dict. Sl. and Cant.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1835		G. Kent Modern Flash Dict.
1848		Flash Dict. in Sinks of London Laid Open.

2. one’s bill, the credit one has run up; usu. in a public house or bar.

1859		G.A. Sala Gaslight and Daylight 84: You would be astonished at the number of portraits [...] which adorn that apartment [i.e. a publican’s sitting-room]. Has the blushing canvas blotted out the sins of the slate?
1884		Sporting Times 20 Sept. 2/5: A poetical publican [...] keeps what is vulgarly known as a ‘slate;’ but he calls it ‘rosemary’ because, he says, it is for remembrance.
1885		Bulletin (Sydney) 19 Sept. 22/3: We say it without fear of contradiction, Billy was as square as a chessboard. He was no chump. He never killed a man without cause. He never forgot to settle his score on the slate.
1893–4		H. Lawson ‘Stiffner and Jim’ in Roderick (1972) 126: ‘How’s the slate?’ [...] ‘Oh, well, we’ll call it thirty bob.’.
1905		Sporting Times 11 Feb. 2/5: The copster leads an active life, / And won’t allow no slates: / ‘Pay up, without deceit or strife / Those merry little—spondulicks, or / you’ll have a man in nex’ week.’.
1929		J.B. Booth London Town 213: I win tree, four tousand pound! [...] I ’ave no more slates!
1933		Townsville Daily Bulletin 3 Aug. 5/1: ‘Tis a sl;ate they have, me bhoy, and what would jim Murphy be doin’ [...] if the name of Sardine kelly was not well inscibed upon that slate.
1964		J.A. Lee Shiner Slattery 41: We’ll get one on the slate.
1970		C. Brown Down All the Days 143: Put that on the slate, me little dote.
1980		A. Payne ‘All Mod Cons’ in Minder [TV script] 56: And it’s about time you settled your slate.
2024		J. Meades Empty Wigs (t/s) 694: I impulse bought green tomatoes, black olives, halloumi, smoked roe, pitta bread. I put it on the slate.

3. in pl., the brains .

c.1893

A. Chevalier ‘’E Ain’t Got the Shadder of a Notion!’ 🎵 But 'e ain't got the shadder of a notion! / ’E’s jest abart as simple as a kid! / I fink ’e’s short in ’is slates above.