In the late Middle Ages, women wore tightly laced bodices stiffened with paste to control and smooth their figures. In the 16th century, however, as the great voyages of discovery across the Atlantic revealed teeming new whale fisheries and rich silks and velvets requiring firmer foundations were imported from Italy and Spain, whalebone became a popular and common material for shaping both body and clothing. Also known as baleen, whalebone is not a bone at all, but the keratinous material found around the upper jaws of baleen whales, used to filter plankton and krill. It is robust but flexible, and can be cut into very narrow strips along the grain. Whalebones were inserted into the lining of outer garments, creating whalebone bodices or "bodies" that molded the torso into a rigid and conical V-shape. In the 17th century, these whalebone linings became distinct, separate understructures, known as "stays." The word corset was not used in its modern sense until the early 1800s, when corsetry—and the pronounced hourglass figure it created—came to dominate both fashion and social discourse on women's health and morality.
Whalebone was replaced by cheaper flat spiral-steels at the beginning of the 20th century, and the corset gave way to lighter girdles in the 1920s and 1930s, but in all its forms, corsetry was worn by most women from youth to old age and across social classes until the 1960s. It was only then that foundation-wear was replaced by diet and exercise as a method of figure control—along with a little help from tensile new fabrics such as Lycra.
The images in this slideshow are photographs of pieces from the extensive collection of undergarments held by the Victoria and Albert Museum in London and have been published in my book about the museum's collection, Underwear: Fashion in Detail.
Click here to read a slide show on corsets.