The Carpenter's Maggot

I have in my possession a MS. tune called the "Carpenter's Maggot," which, until within the last few years, was played (I know for nearly a century) at the annual dinner of the Livery of the Carpenters' Company. Can any of your readers inform me where the original is to be found, and also the origin of the word "Maggot" as applied to a tune?