Mule is a style of shoe that has no back or constraint around the foot's heel. Mules have a history going as far back as Ancient Rome, even though they were not popularly worn until sixteenth-century Europe. There, mules were bedroom slippers and not worn in public. Through the centuries, mules have changed in style and purpose and are no longer just boudoir shoes but are worn at any time, for any occasion. In addition to Western examples, mules come from cultures such as Turkey and Egypt, and appear in popular culture, from famous paintings to iconic celebrities' shoes. History Etymology and original purpose Mule's etymology comes from Ancient Rome. In Ancient Rome, the phrase "mulleus calceus" [mullet shoe] was used to describe the red or purple shoe worn by the three Roman senators and later higher magistrates. In 16th century Europe and France, the Latin root word "mule" was used to refer to both backless shoes and slippers. Mules of the 16th century to the 19th century were bedroom or boudoir slippers worn inside and not out in public. Accordingly, mules were worn with dressing gowns and typically matched the loose outfits by having the same comfort. The early mules did not have any distinguishable features. This style of shoe has a storied history: when Comtesse d’Olonne, the risqué society beauty, wore a soft red pair of mules to church in 1694 – daringly peeping from beneath her richly-embellished skirt – it paved the way for the style. History of their popularity While mules have been worn since the 15th century to the present day, their popularity has not always been constant. They were typical indoor shoes for both men and women in the early 1700s. By the 1720s to the end of the century, mules were the most popular indoor slipper. Fashion plates that exist from the end of the 1790s describe women wearing mules but are not seen due to the long lengths of the contemporary petticoats. Therefore, they were popular by the end of the 1700 but not as visible. In the beginning of the 1800s mules went out of style. In the mid to early 1800s, they rose in popularity again. In the 1860s, prostitutes wore mules in the brothels. The public avoided wearing them. In the late 20th century, mules were again in fashion as they embraced the trends. They were especially popular during