To be like a butcher’s dog, i.e. lie by the beef without touching it; a simile often applicable to married men.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Busy * Butcher’s HorseNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes