“Threshold”
In the old days the floors were made from dirt. Only the wealthy had something other than dirt, hence the saying “Dirt poor.” The wealthy had slate floors that would get slippery in the winter when wet. So they spread thresh on the floor to help keep their footing. As winter wore on, they kept adding more thresh until when the door was opened, it would all start slipping outside. A piece of wood was placed at the doorway, hence a “Threshold.”
Ron Bebbington