A cake made of treacle, flour, and grated ginger; also money. He has the gingerbread; he is rich.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Ginger-pated * Gingerbread WorkNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes