The name Duffel comes from the town in Belgium of the same name where the thick cloth used for military blankets and soldiers' kit rolls. More recently, a duffel bag typically refers to the specific style of bag, though the phrase may also be used to refer to any large generic holdall or a bag made of thick fabric.
These early types of duffel bags were usually "army green" in color, of a cylindrical shape, and closed through a drawstring system at the top.