Green’s Dictionary of Slang

(UK Und.) a criminal trick designed to feed a dog and an additional man for nothing, when food has to be purchased per head (see cit. 1788).

1781		G. Parker View of Society II 80: This trick was once attempted upon a landlord who was a man of the world, and up to their gossip. He informed them that he should charge them only sixpence a-head, and sent them in part of a cold round of beef. He watched them, and saw them give the counterfeit sick man about a pound of beef and another to the Buffer under the table. When they called to know what was to pay, he told them two shillings for eating, for he would be paid a sye-buck a-piece, and would stand no Hook and Snivey, or Nix the Buffer.
c.1786		Grose Classical Dict. of the Vulgar Tongue ms. additions n.p.: Hook and Snivey, with Nix the Buffer. This rig consists in feeding a man & a dog for nothing & is carried on by three men, one of whom pretends to be so sick that he cannot eat. The other two make a bargain with a Publican for their Dinner, & when he is out of sight feed their pretended Sick Comrade & the Dog Gratis.
1788, 1796		Grose Classical Dict. of the Vulgar Tongue (2nd, 3rd edn) n.p.: Hook and Snivey, with Nix the Buffer. This rig consists in feeding a man and a dog for nothing, and is carried on thus: Three men, one of who pretends to be sick and unable to eat, go to a public house: the two well men make a bargain with the landlord for their dinner, and when he is out of sight, feed their pretended sick companion and dog gratis.
1811		Lex. Balatronicum [as cit. 1788].
1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc. 98: Hook and snivvy — practised by soldiers in quarters, when they obtain grub for nix, by connivance with the slavey, or her mistress — or, indeed, the pot-boys and other waiters. A man who orders a steak or joint for one, and makes it serve for two, is at hook and snivvy.
1868		N&Q 4 Ser. 7 Mar. 234/1: This game has been known in the United States for at least fifty years by the name of Hookem Snivvy [...] It is [...] played [...] on the piazzas of the hotels at watering-places.
1890–1904		Farmer & Henley Sl. and Its Analogues III 344/1: Hook and Snivey (or Hookum Snivey), [...] an imposture; specifically, the getting of food under false pretences.