A duffle bag, also known as a duffel bag, is a large, cylinder-shaped bag that's open at one end and closes with a drawstring cinch. The thick waterproof cloth originally used to make the bag was produced in the town of Duffel, Belgium. It is said that in the 1600s, Spanish and Portuguese sailors first adapted the concept of rucksacks into what we think of today as duffle bags by sewing them from the thick fabric of their sails instead of animal skins or wool. Used as a travel bag to carry luggage or equipment, they were soon adapted for the military. Sailors and Marines referred to duffle bags as seabags or "ditty" bags.
These days, the phrase duffle bag also refers to any large gym or "holdall" bag made of thick fabric. These cloth bags are characterized by a rectangular base, a zipper at the top instead of a drawstring at one end, and two handles. Many of these "weekender" bags also come with a shoulder strap.