It is a DASHBOARD !!! Not a FOOT STOOL…
Go back to the time of horse and carriages, a carriages had a piece of wood (BOARD) on the front to act as a barrier against dirt and stones protecting the driver / occupants occupants. When a horse kicked up said stones and dirt it was often referred to being “dashed up”.
So the board on the front gave protection form the horses dashing, Hence DASHBOARD.