Green’s Dictionary of Slang

1. an orig. Irish wager, a rump of beef and a dozen of claret.

c.1786		Grose Classical Dict. of the Vulgar Tongue ms. additions n.p.: Rump & a Dozen; a Rump of beef and a dozen of Claret; an Irish wager, called also Buttock and Trimmings.
1796		Grose Classical Dict. of the Vulgar Tongue (3rd edn) .
1801		Sporting Mag. June XVIII 134/2: The wager of a rump and a dozen between Mr. Giblet, the poulterer, and Mr. Crimp, the fishmonger.
1815		(con. 18C) W. Scott Guy Mannering (1999) 219: ‘I’ll bet a rump and dozen,’ said Pleydell, [...] ‘he has got it in his own pocket.’.
1821		‘An Amateur’ Real Life in London I 333: A rump and a dozen is always a nominal thing. There was no rump [...] and as for the dozen, I believe we drank nearer three dozen of different expensive wines.
1830		Egan Finish to the Adventures of Tom and Jerry (1889) 154: The fat Knight [...] offered to make a match with our heroes for a ‘rump and a dozen!’.
1840		R.B. Peake Devil In London III ii: He get through the world by fair means? Pooh! his supernatural aid given to that booby Pigeon – settled his wager with me! Oh, what a rump-and-dozen will I have down-stairs!
1843		Satirist & Sporting Chron. (Sydney) 4 Feb. 3/2: Sir James Mansfield tried an action on a wager of a rump and a dozen [...] Mr Justice Heath [said that ‘they knew well, privately, that a rump and a dozen meant a good dinner and wine’.
1859		G.A. Sala Gaslight and Daylight 75: Men who yet adhere to the traditional crown bowl of punch, the historical ‘rump and dozen.’.
1871		West Somerset Free Press 8 Apr. 6/3: Lord Mansfield said ‘I do not judicially know the meaning of “a rump and a dozen”,’ but Mr Justice Heath observed that they knew very well privately that rump and a dozen was [...] a good dinner and wine.
1890–1904		Farmer & Henley Sl. and Its Analogues.
1903		Sporting Times 13 June 2/4: If the owner will loan me ‘Vinny’ [...] I am quite prepared to back him [...] for a rump and a dozen.
1933		(con. 1815) Lancs. Eve. Post 13 Sept. 6/3: How many attended the feast of ‘a rump and a dozen’ [...] is not know.
1997		Share Slanguage.

2. a whipping, twelve lashes.

1922

Joyce Ulysses 315: A rump and dozen, says the citizen, was what that old ruffian sir John Beresford called it but modern God’s Englishman calls it caning on the breech.