A long coat worn over a shirt and vest, the justaucorps was one of the most common overgarments worn by men during the seventeenth century. It was also an important garment in the history of men's coats, for it marked an important stage in the long transition from the form-fitting doublet of the fifteenth century to the loosely fitting frock coat of the nineteenth century.
By the mid-seventeenth century people across Europe were breaking from the stiffness and excessive ornamentation of sixteenth-century fashion and seeking more comfortable garments with longer, more elegant lines. Men began to wear a long garment, based on the doublet, that fit closely in the shoulders and sleeves, but flared outward at the waist and hips. Gradually this collarless garment, called a justaucorps (or justacorps), reached all the way to the calves. The lower part of the garment, called the skirt, might consist of several panels that flared outward over the breeches. The justaucorps was often fastened only at the neck, and gaped open in an inverted V shape.
The justaucorps was a flexible garment that was altered to fit the fashions of the day. It might have embroidered designs at the hem and the sides, and could be made of either plain wool or sumptuous velvet or silk to suit the wearer's tastes. By the eighteenth century the justaucorps featured wide cuffs and stiffened skirts. Eventually the justaucorps would transform into the collared frock coat, the precursor to the modern suit coat.
Bigelow, Marybelle S. Fashion in History: Apparel in the Western World. Minneapolis, MN: Burgess Publishing, 1970.
Payne, Blanche, Geitel Winakor, and Jane Farrell-Beck. The History of Costume. 2nd ed. New York: HarperCollins, 1992.