During the middle-ages it was common for the floors of buildings to be no more than compacted earth. To stop the floor getting muddy in wet weather and to insulate the rooms, rushes or hay were put down (sometimes mixed with herbs and flowers to freshen the air). This floor-covering was known as thresh and a piece of wood or stone put across the bottom of a doorway to keep the thresh inside was known as a threshold.
Seats were not provided in church until the 15th century and even if the floors were flagged the excessive cold after long standing and the kneeling required during devotions necessitated the floor being covered.
The renewal of the rushes at the church commonly coincided with the Saint’s Day to which the church was dedicated and the corresponding “Wake,” the custom quickly developed into a part of the religious festival.