Liz Says: Sleep Dresses what a comfortable way to slip into bed. Nightgown, now the term for women's or girls' garments worn to bed, is historically a somewhat confusing term. From the sixteenth through eighteenth centuries, it was a man's loose gown. In the seventeenth and eighteenth centuries, it was a woman's informal day dress-which was, as the name implies, originally an evening dress-hence women might quite modestly go to church in their nightgowns. While authorities believe that for much of Western history no specialized clothing-and sometimes no clothing-was worn for sleep, by the sixteenth century, nightclothes closely related to basic daywear had been adopted by both sexes.