Green’s Dictionary of Slang

Dunbar wether n.

[the fishing trade of Dunbar, Scotland + SE wether, a castrated ram]

a red herring.

[UK]Barrère & Leland Dict. of Sl., Jargon and Cant.
[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]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’.
[UK]Exeter & Plymouth Gaz. 24 Dec. 4/2: Herrings served as ‘Norfolk capons,’ ‘Digby chickens,’ ‘Dunbar wethers,’ or ‘Gowrock hams’.