Renaissance Clothing and the Evolution of Underwear
While times and clothes have changed so often and so radically, most of the concepts that birthed various articles of clothing have more or less remained the same. The concept behind underwear was to uphold a degree of modesty. Like now, back then there was no universal underwear rule and people wore what was comfortable, available-or nothing at all.
Ancient Bare Necessities
Not much documentation or clothing survives (woolen and linen garments rot after a few hundred years and no one ever thought writing about underwear was important). Getting a definite idea of what people wore beneath their clothes before medieval times can only come from what surviving mosaics or works of art there are, which aren't yet very realistic.
But in ancient times, Imperial Rome set the trend in everything, including what one wore beneath one's outer wear. Men and women alike were known to wear loin-cloths, probably made of linen. Women might have worn a lengthy band wrapped around their chests called a strophium or mamillare.
Medieval Clothing and Underpants
When the Middle Ages began, medieval under clothes for men were called braies or breeches. Men held their loose drawers in place with a drawstring or a belt. There is little to no evidence of under clothing for medieval women. The ankle-length dresses of medieval women and layers of other articles of clothing make it impossible to determine. However, both men and women wore hose, medieval stockings commonly made of wool, not very stretchy but did the trick against cold weather. Nevertheless, men didn't have pants to wear yet at the time and only wore hose underneath long tunics.
What is known about 14th-century medieval under clothes for women is the chemise, a loose or slightly figure-fitting garment that goes under the kyrtle, an under gown that can have a train for formal occasions. The chemise would continue be worn well into the next few centuries.
Corset - Breathe Not
While the chemise slowly varied in form and neckline, square or high by the 17th century, the corset came into use in the late 14th to early 15th centuries in France and England. As medieval dresses evolved toward more form-fitting designs, the corset helped define the female waist and breasts. By the 1600s Renaissance dresses had corsets that were shorter and might have a stiff busk at the center. Since their inception, the corset and the chemise were already considered among of the staples of women's clothing.
Men, on the other hand, made improvements on the breeches and the hose, which remained staples in both medieval and Renaissance wardrobes. As new materials were introduced and dyes became the trend, these clothing articles upgraded considerably.