This site is in danger of going away; please consider the Donate link above...
The head. His garret, or upper story, is empty, or unfurnished; i.e. he has no brains, he is a fool.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Garnish * Garret ElectionNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes
Buy a modern reprint of this book from Amazon CA; US;
Francis Grose was independently wealthy, having inherited money from his father, a jeweller. Finding himself overspending, he published a number of books; his Provincial Glossary seems to have been the starting-point for the Vulgar Tongue reproduced here.