E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
One of the seniors or elders. Now applied to a class of magistrates in corporate towns. In London an alderman is the chief magistrate in a ward appointed by election. There are also aldermen of the County Council.
A turkey is called an alderman, both from its presence in aldermanic feasts, and also because of its red and purple colours about the head and neck, which make it a sort of poultry alderman.
An alderman in chains, by a similar effort of wit, is a turkey hung with sausages.