Green’s Dictionary of Slang

1. anything unpleasant that emerges after a situation had been supposedly settled; cites 1707, 1834 pun on clap n. (1)

1707		Farquhar ‘To a Gentleman who had his Pocket Pick’d [...] by a Mistriss’ in A. Carpenter Verse in Eng in 18C Ireland (1998) 65: You say you fear some After-clap.
1710		J. Strype History of [...] Edmund Grindal 103: Some After-Clap of News, which might clash with, and confute the first Tidings.
1741		Witchcraft of Love 31: You said I should have her, if my Father would settle so and so, and now you come with your After-clap of consider’d, and changed your Mind.
1775		J. Fletcher Zelotes & Honestus Reconciled xix: With respect to that gentleman’s character, this after-clap does not alter my thoughts of it.
1785		W. Forbes Dominie Deposed 5: If such things be done with speed, Their safe, ’tis help in time of need, No after claps.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1834		Ely’s Hawk & Buzzard (NY) 15 Mar. 3/1: Miss M.R. be careful of after claps.
1842		Flash 14 Aug. n.p.: Becky, for fear of afterclaps, then betook herself to French Henry’s.
1846		Swell’s Night Guide 109/1: After-clap, any disagreeable affair attending an action, see clap, pox.
1856		Liverpool Mail 29 Mar. 5/1: Peculiarly unpleasant after-claps in the shape of inexorable demands for heavy arrears.
1872		Manchester Eve. News 22 Feb. 4/3: I may hope and pray that the civilian afterclaps of the late election may be as mild [...] in their effects upon disobedient voters as the ecclesiastical [...] penalties have been upon your truly.
1887		Wkly Messenger (St Martinville, LA) 13 Aug. 2/2: An afterclap always accompanys such events [...] he had just secured warrants for our arrests.
1890		Shoreditch Observer 9 Aug. 3/3: After-Claps [...] There had been a dispute [...] and Mrs Peck alleged that Newsman struck her several violent blows.
1894		Durham Dly Globe (NC) 19 Jan. 2/2: He is permitted to scribble upon the pages of the weekly afterclap of a former defunt daily newspaper.
1903		Goodwin’s Wkly (Salt Lake City, UT) 12 Dec. 7/1: But now comes the afterclap. Bill is re-elected.
1917		Polk Co. Republican (Duck Town, TN) 21 Dec. 1/3: When a committee [...] usurps the right of the people, there is pretty apt to be an afterclap.
1921		Eve. Public Ledger (Phila., PA) 26 Sept. 7/3: It is an afterclap of the August Furniture Sale [...] enormous selling from day to day.

2. a bill that is presented after the first has already been paid.

1781		J. Morley Scrophulous Disorders 87: Persons wishing to consult me may be afraid, lest, as I am not regularly feed, should come with the After-Clap of a long Bill.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1793		J. Caulfield Blackguardiana.
1811		Lex. Balatronicum.
1827		Guards 46: [E]xpensive dinners are given, which are as often paid for by the invited as the inviters — by what is vulgarly called afterclaps.