Green’s Dictionary of Slang

topping n.2

[top v.3 ]

1. execution by hanging; also attrib.

[UK]H.T. Potter New Dict. Cant (1795).
[UK]G. Andrewes Dict. Sl. and Cant.
[Aus]Vaux Vocab. of the Flash Lang. in McLachlan (1964) 238: dues [...] like many other cant terms, it is not easily explained on paper: for example, speaking of a man likely to go to jail, one will say, there will be quodding dues concerned, of a man likely to be executed; there will be topping dues [etc.].
[UK]Flash Dict.
[UK]G. Kent Modern Flash Dict.
[UK]Flash Dict. in Sinks of London Laid Open.
[US]R.J. Tasker Grimhaven 28: Do they talk about topping?
[UK]F. Norman Bang To Rights 173: The day after a topping it is all forgotten and nobody ever speaks of it again.

2. suicide; also attrib.

[UK]J. Cameron Vinnie Got Blown Away 11: Put him on the topping list, meant they looked in once a night if you’re lucky.
[Aus]P. Temple Dead Point (2008) [ebook] It’s a bit like suicide [...] Toppin’s a bit like hide and seek, know what I mean?

In compounds

topping cheat (n.) [cheat n. (1); lit. ‘hanging thing’]

(UK Und.) the gallows.

[Ire]Head Canting Academy (2nd edn) n.p.: Topping-cheat The Gallows.
[UK]B.E. Dict. Canting Crew [as cit. 1674].
[UK]New Canting Dict. [as cit. 1674].
[UK]Bailey Universal Etym. Eng. Dict. [as cit. 1674].
[UK]Grose Classical Dict. of the Vulgar Tongue.
[UK]Lex. Balatronicum.
[UK]Egan Grose’s Classical Dict. of the Vulgar Tongue.
[UK]Lytton Paul Clifford I 28: If you cheats toppingly, you may laugh at the topping cheat.
topping cove (n.) [cove n. (1)]

1. (UK Und.) a hangman.

[Ire]Head Canting Academy (2nd edn) 181: Toppin Cove The Hangman.
[UK]B.E. Dict. Canting Crew n.p.: Topping-Cove c. the hangman.
[UK]New Canting Dict. [as cit. c.1698].
[UK]Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
[UK]B.M. Carew Life and Adventures.
[UK]Grose Classical Dict. of the Vulgar Tongue.
[UK]H.T. Potter New Dict. Cant (1795).
[UK]G. Andrewes Dict. Sl. and Cant.
[UK]Lex. Balatronicum.
[UK]Egan Grose’s Classical Dict. of the Vulgar Tongue.
[UK]G. Kent Modern Flash Dict.
[UK]Flash Dict. in Sinks of London Laid Open.
[US]Matsell Vocabulum.
[Aus]Crowe Aus. Sl. Dict. 87: Topping Cove, the hangman.

2. see also compounds under topping adj.

topping match (n.)

a judicial hanging.

[UK]Flash Mirror 21: Drags let our for parties going to [...] topping-matches, and other amusements.
topping shed (n.)

that part of a prison in which the gallows is kept.

[UK]E. Raymond Marsh 317: ‘Where’s the condemned cell?’ ‘Next to the toppin’ shed, matey.’.
[UK]‘Charles Raven’ Und. Nights 106: P.O. Ferris was the officer in charge of E wing, which contains the chokey [...] and the topping (or execution) shed.
[UK]F. Norman Guntz 45: A man in the topping shed on the morning of his judicial murder is often dragged to the scaffold by his barnet.
[UK] in G. Tremlett Little Legs 166: Years ago it [i.e. Pentonville prison] used to have a topping-shed.
[UK]Guardian G2 29 Jan. 6: The ‘topping shed’ where James Hanratty was hanged 40 years ago has been demolished.