Green’s Dictionary of Slang

1. buttermilk or whey or any thin, non-alcoholic drink.

c.1566		Harman Caveat for Common Cursetours in Viles & Furnivall (1907) 83: lap, butter milke or whey.
1592		Groundworke of Conny-catching n.p.: [as cit. c.1566].
1608		Dekker Lanthorne and Candle-Light Ch. 1: If we mawnd Pannam, lap, or Ruff-peck.
1611		Middleton & Dekker Roaring Girle V i: A gage of ben rom-bouse [...] Is benar then a caster, / Peck, pennam, lap, or popler.
1641		R. Brome Jovial Crew II i: Here’s Pannam and Lap, and good Poplars of Yarrum, / To fill up the Crib, and to comfort the Quarron.
1665		Head Eng. Rogue I 50: Lap, Pottage.
1674		‘The Beggars Curse’ Head Canting Academy (1674) 14: If we maund Pannam, lap, or ruff peck.
1688		R. Holme Academy of Armory Ch. iii item 68c: Canting Terms used by Beggars, Vagabonds, Cheaters, Cripples and Bedlams. [...] Lap, Butter-Milk or Whay.
c.1698		B.E. Dict. Canting Crew n.p.: Lap c. Pottage, Butter-milk, or Whey.
1707		Rum-Mort’s Praise of Her Faithless Maunder in Dodsley (1826) 36: Grannam ever fill’d my sack / With lap and poplars held I tack.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
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.
1815		(con. 18C) W. Scott Guy Mannering (1999) 148: And the gentry had kind hearts, and would have given both lap and pannel to ony poor gipsy.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1833		‘The Christening of Little Joey’ in Corinthian in Spedding & Watt (eds) Bawdy Songbooks (2011) IV 45: They back again soon pik’d it, / To have a dish of lap.
1848		Flash Dict. in Sinks of London Laid Open.
1859		Matsell Vocabulum.

2. liquor in general.

c.1614		Beaumont & Fletcher Bonduca I i: A pretty valiant fellow, Die for a little lap and lechery?
1719		in D’Urfey Pills to Purge Melancholy V 63: He call’d so fast for Lap and Smoak.
1725		New Canting Dict. n.p.: lap [...] strong Drink of any Sort.
a.1790		H.T. Potter New Dict. Cant (1795).
1809		G. Andrewes Dict. Sl. and Cant.
1840		Flash Mirror 19: G. Guttle [...] has just opened a slap up grub and bub shop [...] (for ready rag only), where he sells panum, lap and peck of every sort.
1849		Era (London) 3 June 3/4: It was smokin’ hot, and the rush for lap of any kind and all kinds was tremenduous [sic].
1858		A. Mayhew Paved with Gold 353: Instead of getting to some libb-ken, on the main toper, where a drop of lap could be had, you’re sticking to the back drums.
1864, 1867		Hotten Sl. Dict.
1873		Sl. Dict. 212: Lap liquor, drink. lap is the term invariably used in the ballet girl’s dressing-room for gin.
1889		‘’Arry on the Ice’ in Punch 23 Feb. 85: Who wants light when you’re out for a lap and a lark?
1899		R. Whiteing No. 5 John Street 229: She is prepared, I think, to accept [...] I was once a shop-walker, and fell through ‘lap,’ for which read ‘liquor’.
1929		N.Y. Sun. News 3 Nov. in AS VI:2 159: lap is liquor.
1933		‘William Juniper’ True Drunkard’s Delight.
1934		H. Sebastian ‘Negro Sl. in Lincoln University’ in AS IX:4 288: lap (also juice). General name for alcoholic liquor.

3. soup.

1665		in R. Head Eng. Rogue (1874) Pt 1 Ch. v 50: Lap, Pottage [F&H].
1728		Defoe Street Robberies Considered 33: Lap, Spoon-meat.
1754		Scoundrel’s Dict. 18: Pottage – Lap.

4. (also brown lap) tea.

1722		‘Whipping-Tom’ Universal Poison, or the Dismal Effects of Tea II 12: Our Exchange Girls, [...] are Devils at this Sort of Lap, guzzling it down as fast as a drunken Tarpaulin will a Can of Flip.
1789		G. Parker Life’s Painter 139: The christ’ning being o’er, / They back again soon pik’t it, / To have a dish of lap, / Prepar’d for those who lik’t it.
1836		W.H. Smith ‘The Thieves’s Chaunt’ in Farmer Musa Pedestris (1896) 121: For she never lushes dog’s-soup or lap, / But she loves my cousin the bluffer’s tap.
1846		Swell’s Night Guide 65: ’Spose I can have some hot pawney, and crack slums to fake a bag o’sweet lap? [Ibid.] 71: They took their tightener, – viz., a bag of brown lap, a brace of pickled deserters, a dab of smeerums, a nob o’pannum.
1909		J. Ware Passing Eng. of the Victorian Era.