Selvage denim (also called selvedge denim) is a type of denim which forms a clean natural edge that does not unravel. It is commonly presented in the unwashed or raw state. Typically, the selvage edges will be located along the outseam of the pants, making it visible when rolled into a cuff.
The word selvage comes from the phrase “self-edge” and denotes denim made on old-style shuttle looms. These looms weave fabric with one continuous cross thread (the weft) that is passed back and forth all the way down the length of the bolt of fabric. As the weft loops back into the edge of the denim it creates this “self-edge” or selvage. Selvage is desirable because it can’t fray, unlike most denims, which have separate wefts that leave an open edge and must be stitched. While shuttle looming is a more time-consuming weaving process, another benefit is that it produces denim with a tighter weave and heavier weight that lasts longer.
And, as a bonus for reading, you have a new Scrabble word: “weft”.