Field Lane duck, n. — Green’s Dictionary of Slang

Field Lane duck n.

[Field Lane, which once linked Holborn to Clerkenwell; ‘Field Lane is a low London thoroughfare, leading from the foot of Holborn Hill to the purlieus of Clerkenwell. It was formerly the market for stolen pocket-handkerchiefs’ (Hotten, 1864); note Portfolio (19 Oct. 1826): ‘Jones’, with oxcheek at twopence a plate, in St Giles, and ‘Haycraft’, with his sheeps heads in Field Lane’]

a baked sheep’s head.

1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1809		G. Andrewes Dict. Sl. and Cant.
1811		Lex. Balatronicum.
1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc.
1825		W.T. Moncrieff Works III (1851) 135: A Sheep's head otherwise a Field lane Duck, otherwise The One Eyed joint, otherwise a Claretted James, otherwise Sanguinary Jacobus, otherwise a Pastoral Countenance, otherwise a Peaceful Profile — that man is to be pitied, who has not luxuriated on the delicacies of one of these, hot from the pan.
1835		G. Kent Modern Flash Dict.
1848		Flash Dict. in Sinks of London Laid Open.
1854		Life & Battles of Yankee Sullivan 14/2: Lane again gave his adversary [whose head exhibited a very lively representation of a ‘Field Lane duck, alias a b — y jemmy,’] a poke in the breadbasket and retired.
1860		Hotten Dict. of Modern Sl. etc. (2nd edn).
1864, 1867, 1870		Hotten Sl. Dict.
1874		Newcastle Courant 10 Apr. 3/6: A ‘field lane duck’ is a baked sheep’s head.
1888		Gloucs. Echo 19 Mar. 3/6: A Field Lane Duck is a baked sheep’s head.
1882		Sydney Sl. Dict. (2 edn) 4: Field-lane Duck - A baked sheep’s head.
1893		Western Mail 21 Dec. n.p.: A 'German duck,' or 'Field-lane duck,' is in ordinary eating-house mock heroic for a sheep's head stewed with onions.
1897		N. Platte Semi-wkly Trib. (NE) 14 May 3/3: ‘Field Lane ducks,’ meaning boiled sheepshead and onions.
1901		Minneapolis Jrnl (MN) 13 Apr. 8/3: In London a sheep’s head stewed with onions is called a ‘field lane duck’.
1909		J. Ware Passing Eng. of the Victorian Era.
1913		Nottingham Eve. Post 22 Sept. 3/4: The londoner is very prolific in these nuicknames. A baked sheep’s head [is] a ‘Field Lane duck’.
1919		Free-Trader Jrnl (Ottowa, IL) 8 Dec. 7/3: Gastronomic Animals [...] A Fieldlane duck is a baked sheep’s head.