E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Gilt (g hard).
To take the gilt off the gingerbread. To destroy the illusion. The reference is to gingerbread watches, men, and other gilded toys, sold at fairs. These eatables were common even in the reign of Henry IV., but were then made of honey instead of treacle.