Green’s Dictionary of Slang

1. (UK/US Und.) one who knocks a person down, at which a confederate appears and, under pretext of ‘helping’ robs the victim.

a.1790		H.T. Potter New Dict. Cant (1795) n.p.: floorers fellows who throw persons down, after which their companions (under pretence of assisting and detecting the offender) rob them in the act of lifting them up.
1809		G. Andrewes Dict. Sl. and Cant.
1821		Flash Dict.
1835		G. Kent Modern Flash Dict.
1848		Flash Dict. in Sinks of London Laid Open.
c.1850		Duncombe New and Improved Flash Dict.
1859		Matsell Vocabulum 33: floorers or trippers Fellows that cause persons to slip or fall in the street, and then, while assisting them up, steal their watch or portmonnaie. They are sometimes called ‘rampers.’.
1895		Crowe Aus. Sl. Dict. 29: Floorers, or Trippers, or Rampers, robbers who cause people to slip on the streets and then rob them.

2. a blow that will knock its recipient down; thus anything, e.g. a piece of bad news, that renders its recipient ‘floored’; also in fig. use.

1818		N.-Y. Eve. Post 17 Aug. 2/1: we do not understand the technical phrases he makes use of, such as nobbing each other in fine style — a good set-to — a clean hit — a facer — a floorer and unable to come-to in time, &c, &c. He had better make his complaint to the police office, whose business it is to attend to such affairs.
1819		‘One of the Fancy’ Tom Crib’s Memorial to Congress 20: Foi in these Fancy times, ’tis your hits in the muns / And your choppers, and floorers, that govern the Funds.
1821		‘An Amateur’ Real Life in London I 229: ‘Take that, then,’ said the other, and gave him a floorer; but he was prevented from falling by those around him.
1832		Egan Bk of Sports 52: A floorer, what an author would term a climax, and the actor a denoument.
1835		J.C. Apperley Nimrod’s Hunting Tour (1874) 206: Being pumped out by the pace, the young one got a floorer.
1840		T. Hood Friend in Need in Works (1862) V 330: ‘My eyes, what a floorer!’ repeated the Quaker, as the Young ’Un went down.
1854		‘Cuthbert Bede’ Adventures of Mr Verdant Green (1982) II 171: The enquiry for his ‘college’, was, in the language of his profession, a regular ‘floorer’.
1861		H.C. Pennell Puck on Pegasus 20: What a floorer to my hopes is this performance on the ropes!
1873		Sl. Dict. 165: Floorer [...] Often used in reference to sudden and unpleasant news.
1879		‘’Arry on ’igh Art’ in Punch 1 Feb. 42/2: Such togs are a floorer to me.
1890		‘Rolf Boldrewood’ Colonial Reformer I 141: It won’t do Bouncing Bob any harm to get a floorer or two.

3. (UK Und.) a judge in the act of passing the sentence of death.

c.1850

Duncombe New and Improved Flash Dict.