The best used to be made at Grantham, and Grantham gingerbread was as much a locution as Everton toffy, or tuffy as we used to call it in the first half of the nineteenth century.
(g soft). Brummagem wares, showy but worthless. The allusion is to the gilt gingerbread toys sold at fairs.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894