Until the 18th century, men’s pants as we know them today didn’t exist. At that time, well-dressed men wore knee breeches that reached just below their knees, with long hose to cover the rest of their legs.
Then in 1789, when the French Revolution began, men who supported the Revolution gave up the knee breeches worn by the king and his supporters, and started to wear trousers instead. These revolutionaries soon became known as sans-culottes, which in French means “without breeches.”
Trousers didn’t catch on in America until around 1810. The first American president to wear long trousers was James Madison, the fourth president.