A court formerly held at a fair on St. Giles's Hill, near Winchester. It was originally authorised by the Bishop of Winton from a grant of Edward IV. Similar courts were held elsewhere at wakes and fairs for the rough-and-ready treatment of pedlars and hawkers, to compel them and those with whom they dealt to fulfil their contracts. (French, pied poudreux, dusty foot. A vagabond is called in French pied poudreux.)
Have its proceedings disallowed or Allowed, at fancy of pie-powder.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894