Green’s Dictionary of Slang

1. a workhouse where one is fed without performing the usual mandatory labour.

1859		Hotten Dict. of Modern Sl. etc. 47: GRUBBIN-KEN [...] a workhouse.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor III 406/1: I know all the good houses, and the tidy grubbikens, – that’s the unions where there’s little or nothing to do for the food we gets.
1864		Hotten Sl. Dict. 148: GRUBBING-KEN [...] a workhouse.
1873		Sl. Dict. 183: Grubbing ken [...] a workhouse.
1882		Dundee Courier (Scot.) 8 Aug. 7/4: I was not a frequenter of grubbing kens.
1895		Belfast News-Letter 26 Dec. 7/2: Jimmy the Needles has pegged out in the grubbing-ken (workhouse|) at Bristol.

2. a cookshop.

1831		Quizzical Gaz. 24 Sept. 34/1: The walking Bundle of Fat may be seen, (only sixpence each,) and consulted with, as to the terms on which his gross Body will be disposed of, by applying at Dirty Dick’s, Grubbing Ken, Lambeth Marsh.
1872		Bailey’s Mag. Feb. 202: An eating-house is a grubbing-ken.
1873		Sl. Dict. 183: Grubbing ken [...] a cook-shop.