answer:I think of a duvet as being a comforter, and what you describe is the duvet cover. Hotels were not washing the entire bedspread (the old fashioned thin, gauzy bottomed flowery things) every time, and news magazine shows (ie 20/20) did studies with ultra violet light (or whatever highlights bodily fluids) and showed semen, etc on the bedspreads. They interviewed hotel management who admitted that the spreads were not laundered each time as they were too bulky, and therefore, the prospect of laying on or under fabric covered in dried semen is pretty unappealing. The bleached-white, washed fresh for each guest duvet cover popular today (and more aesthetically appealing, too, IMHO), is better, more sanitary and more appealing.