Green’s Dictionary of Slang

Yarmouth capon n.

also Norfolk capon
[the local fishing industry]

1. a red herring.

[UK]Fuller Worthies (1840) II 447: ‘A Yarmouth capon’. That is, a Red-herring [...] I believe few Capons (save what have more fins than feathers) are bred in Yarmouth. But, to countenance this expression, I understand that the Italian Friers (when disposed to eat the flesh on Fridays) call a Capon ‘piscem è corte,’ (a fish out of the coop).
[UK]J. Ray Proverbs 245: A Yarmouth Capon. That is a red herring.
[UK]B.E. Dict. Canting Crew n.p.: Yarmouth capon a red Herring.
[UK]New Canting Dict. [as cit. c.1698].
[UK]Grose Classical Dict. of the Vulgar Tongue n.p.: Norfolk capon, a red herring. [Ibid.] Yarmouth capon, a red herring.
[UK]H.T. Potter New Dict. Cant (1795) n.p.: Norfolk capon red herring.
[UK]G. Andrewes Dict. Sl. and Cant [as cit. a.1790].
[UK]Lex. Balatronicum [as cit. 1785].
[UK]‘Jon Bee’ Dict. of the Turf, The Ring, The Chase, etc.
[UK]Swell’s Night Guide 126/2: Norfolk capon, [...] a red herring.
[UK]Duncombe New and Improved Flash Dict.
[UK]E. de la Bédollière Londres et les Anglais 319/1: yarmouth capon, [...] hareng.
[UK]Hotten Sl. Dict.
[UK]Newcastle Courant 10 Apr. 3/6: ‘Gourock hams’ or ‘Norfolk capons’ are red herrings.
[US]N. Platte Semi-wkly Trib. (NE) 14 May 3/3: ‘Digby chickens,’ ‘Glasgow magistrates,’ ‘Gourock hams,’ ‘Dunbar wethers,’ ‘Norfolk capons’ all meaning red herrings.
[US]Reno (NV) Eve. Gazette 28 Apr. 2/2: Red herrings are ‘Glasgow magistrates’ or ‘Norfolk capons.’.
[US]Minneapolis Jrnl (MN) 13 Apr. 8/3: A herring is called in different localities in England a ‘Digby chicken,’ a ‘Norfolk capon,’ a ‘Dunbar wether,’ or a ‘Gourock ham’.
Free-Trader Jrnl (Ottowa, IL) 8 Dec. 7/3: Gastronomic Animals [...] Glasgow magistrates or Norfolk capons are red herrings.
[UK]Exeter & Plymouth Gaz. 24 Dec. 4/2: Herrings served as ‘Norfolk capons,’ ‘Digby chickens,’ ‘Dunbar wethers,’ or ‘Gowrock hams’.

2. a soldier, i.e. his red coat.

[UK]‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc.
[UK]G. Kent Modern Flash Dict. n.p.: Norfolk capon a soldier.
[UK]Flash Dict. in Sinks of London Laid Open [as cit. 1835].

3. a bloater.

[UK]Hotten Dict. of Modern Sl. etc. (2nd edn).
[UK]Sl. Dict.