E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A court held thrice a year before forest verderers by the steward of the court. So called because the swans or swains were the jurymen. (Swans, swains, or sweins, freeholders; Anglo-Saxon, swan or swein, a herdsman, shepherd, youth; our swain.)
This court was incident to a forest, as the court of pie-powder or piepoudre to a fair.