Petticoats were full skirts that women wore beneath another skirt beginning in the fifteenth century. There were several reasons for wearing petticoats. One reason was practical: Petticoats added body to the skirt and kept the women who wore them warm. But wearing petticoats was usually done to keep in fashion, especially in the seventeenth century. Once women quit using farthingales, or stiff hoops, to add body to their skirts, they turned to petticoats to do the job. Petticoats worn for warmth were made of wool or cotton, while those worn for fashion were made of taffeta, satin, linen, or a combination of starched fabrics.
Petticoats were gathered at the waist and flared outward at the hem. Many were highly ornamental, featuring layers of ruffles, trimming, and lace. Most of the trimming was along the bottom edges, the part most likely to be seen. Beginning in the late seventeenth century women pulled up their outer skirts in a style known as mantua, allowing the petticoats to be seen.
Petticoats were first fashionable to see in the seventeenth century, and then they were mostly an underskirt. After the mid-eighteenth century, petticoats were primarily thought of as a form of underwear. They did come back into fashion in the 1950s and were worn under knee-or calf-length skirts to give them volume. In the 2000s, they are occasionally worn for specific occasions, such as square dances.
Some men in the mid-seventeenth century wore something called petticoat breeches. These elaborately tailored breeches featured loose legs puffed out in a skirt that hung to the knees, and were sometimes worn with smaller petticoat skirts around the calves. This strange style was not around for long.
Cunnington, C. Willett, and Phillis Cunnington. Handbook of English Costume in the Seventeenth Century. Boston, MA: Plays, Inc., 1972.
Yarwood, Doreen. The Encyclopedia of World Costume. New York: Charles Scribner's Sons, 1978.