hourglass (n.) Look up hourglass at Dictionary.com
1510s, from hour + glass. Used 19c. in a variety of technical and scientific senses to describe the shape; reference to women's bodies is attested by 1897.
Men condemn corsets in the abstract, and are sometimes brave enough to insist that the women of their households shall be emancipated from them; and yet their eyes have been so generally educated to the approval of the small waist, and the hourglass figure, that they often hinder women who seek a hygienic style of dress. [Mary Ashton Rice Livermore, "The Story of My Life," 1898]