..top of the draped fabric in the back over the rear end. They made the woman look like a piece of upholstery.
Other top skirts were called aprons and they were also draped making the wearer look like a piece of elaborate upholstery.
(The 1868 gown had elaborate trimming front AND back.. but it would move around to just the back very soon. Rght now it still has the ovoid shape of the mid-Victorian crinoline hoop)