Wheat boiled up to a jelly. To simper like a furmity kettle: to smile, or look merry about the gills. [See also FLUMMERY—Liam]
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Furmen * FussNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes