Denim is a rugged cotton

Cotton

Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....

 twill

Twill

Twill is a type of textile weave with a pattern of diagonal parallel ribs . This is done by passing the weft thread over one or more warp threads and then under two or more warp threads and so on, with a "step" or offset between rows to create the characteristic diagonal pattern. Because of this...

 textile

Textile

A textile or cloth is a flexible woven material consisting of a network of natural or artificial fibres often referred to as thread or yarn. Yarn is produced by spinning raw fibres of wool, flax, cotton, or other material to produce long strands...

, in which the weft

Weft

In weaving, weft or woof is the yarn which is drawn through the warp yarns to create cloth. In North America, it is sometimes referred to as the "fill" or the "filling yarn"....

 passes under two (twi- "double") or more warp

Warp (weaving)

In weaving cloth, the warp is the set of lengthwise yarns that are held in tension on a frame or loom. The yarn that is inserted over-and-under the warp threads is called the weft, woof, or filler. Each individual warp thread in a fabric is called a warp end or end. Warp means "that which is thrown...

 threads. This produces the familiar diagonal ribbing identifiable on the reverse of the fabric, which distinguishes denim from cotton duck

Cotton duck

Cotton duck , also simply duck, sometimes duck cloth or duck canvas, commonly called "canvas" outside the textile industry, is a heavy, plain woven cotton fabric...

. Denim has been in American usage since the late 18th century. The word comes from the name of a sturdy fabric called serge

Serge

Serge is a type of twill fabric that has diagonal lines or ridges on both sides, made with a two-up, two-down weave. The worsted variety is used in making military uniforms, suits, great coats and trench coats. Its counterpart, silk serge, is used for linings. French serge is a softer, finer variety...

, originally made in Nîmes

Nîmes

Nîmes is the capital of the Gard department in the Languedoc-Roussillon region in southern France. Nîmes has a rich history, dating back to the Roman Empire, and is a popular tourist destination.-History:...

, France, by the André family.