Reality of life and changes in fashion aesthetics draw interest to more feminine body types rather than standard, streamline, elegant type of average female figure. This more renaissance/baroque look of female figure is a valuable aesthetic concept for fashion figure drawing when femininity is the focus of fashion style. Curvy body style of female figure is often called an hourglass body type due to obvious curvature of this type of figure. Hourglass body type is a style of proportions of human figure within standard 9 heads tall ratio but with more exaggerated contrast between volume of hips, waist line and bust line.
Hourglass fashion figure is true to reality in the sense that there are many real life examples of women with accentuated curvature of body lines. But as an abstract model for an actual type of a female body, an hourglass fashion figure is a subject to certain stylization.
History of aesthetics of hourglass type of female figure goes to prehistoric times and its raw forms could be witnessed in body forms of prehistoric sculptures.
All classic paintings from Sandro Botticelli to Amedeo Modigliani symbolize beauty and classical elegance of curvy female figure in its hourglass type of the body forms.
The whole idea of corset in women's fashion was triggered in renaissance period as a standard of beauty for female figure and remained so for at least four plus centuries (with short exception of Empire fashion).
Gibson girls would be an excellent historical manifestation of hourglass female body type.
Understanding of hourglass female figure is easier if you keep in mind body types of Sofia Loren, Marilyn Monroe, Brigitte Bardot, Gina Lollobrigida rather than Audrey Hepburn or Twiggy.