What is a duffle coat?
duffle coat — This is a single-breasted woolen coat of a straight cut with a hood and characteristic fastening with wooden or bone buttons (toggles).

The name of the coat comes from the Belgian town of Duffel, where the thick woolen fabric from which these coats were originally made was produced. The duffle coat was developed in the late 19th century as part of the winter uniform of the Royal Navy.
The coat's transition into civilian wardrobe staples occurred in the 1950s following the massive sale of military surplus. It became especially popular among students, becoming an integral part of Ivy League style.
Distinctive features
Traditionally, duffle coats are made of dense, double-layered wool, which retains heat well. The inside of the fabric often features a contrasting tartan pattern.

The coat's most recognizable element is the leather or jute cord loops and walrus tusk-shaped buttons. Historically, this design allowed sailors to button and unbutton their outerwear without removing thick gloves.
The hood's voluminous design was originally designed to be worn over a peaked cap. A tab under the neck provides additional wind protection. Other design features include large patch pockets and reinforced shoulder pads (yoke) to prevent the garment from quickly becoming wet in rain and snow.

What to combine with
The duffle coat fits harmoniously into preppy and smart-casual styles. It pairs perfectly with textured knit sweaters, oxford shirts, pleated skirts, and corduroy trousers.

For casual looks, a duffle coat makes a basic pairing with straight-leg blue jeans and a heavy turtleneck. For footwear, rugged styles such as Chelsea boots, brogues, or high-top lace-up boots complement this ensemble.
In a business attire, it's acceptable to wear a duffle coat over a casual wool or tweed suit. However, for a business formal dress code, this coat is considered too casual.