It obtained its name because the meetings of the hundred were…

The Domesday Book shows that Grendon formed part of the Wymersley Hundred, which covered an area of over 52 square miles south of the Nene between Northampton and Wellingborough. It obtained its name because the meetings of the hundred were held in a field called Wymersley Bush near Little Houghton.

The Countess Judith and niece of William the Conqueror was Lord of Wymersley and a substantial landowner in the county through marriage, particularly in Wymersley and the adjoining hundreds of High and Fair Hamfordshoe, (Ecton to Wellingborough) and Spelhoe, (Northampton).