Wikipedia
Petticoat breeches were voluminously wide, pleated pants, reminiscent of a skirt, worn by men in Western Europe during the 1650s and early 1660s. The very full loose breeches were usually decorated with loops of ribbons on the waist and around the knee. They were so loose and wide that they became known as petticoat breeches. They give very much the impression of very baggy loose shorts since they are not gathered at the knee.
They replaced Spanish breeches during the 1650s as the most popular leg wear of most of Western Europe. By the early 1660s, rhinegraves became very popular and soon replaced petticoat breeches.
Usage examples of "petticoat breeches".
He was wearing a light jacket over a silk shirt and petticoat breeches and was carrying buttoned foils under his arm.
He freed the laces with a quick jerk, and the petticoat breeches ballooned to the floor with a whiff of wind.
He was dressed in sailor fashion, with petticoat breeches of duck, a heavy pea-jacket, and thick boots, reaching to the knees.
One of them was a negro, naked to the waist, and the other was a white man in his shirt sleeves, wearing petticoat breeches, a Monterey cap upon his head, a red bandanna handkerchief around his neck, and gold earrings in his ears.