A "dew rag" is a kerchief of absorbent material, usually cotton or nylon, tied around the head for reasons of both style and practicality. The term was allegedly coined by African-American soldiers in the Vietnam War, where the handy little fashion accessories were used to soak up both ambient moisture from the super-humid jungles and their own sweat. Since most infantrymen wore their hair fairly closed-cropped if not shaved off entirely, the dew rag had a tertiary use of shielding their scalps from the blazing oriental sun. Often confused with bandanas (more suited for keeping out dust than dew), a true dew rag covers the entire crown of the head and ties together at the back.
Like the humble cloth workman's cap that found its prominence after the Civil War and well into the 20th century, the dew rag, along with the baseball cap and overalls, remains a mainstay of American blue-collar culture. It has been tied on by construction laborers, biker nomads, and inner-city gangsters, playing the part of an expression of loyalty, a convienient windblocker, a robust reminder of the wearer's insatiable joie de vivre, or a cheap alternative to getting a real hat. Although many dew rags geared toward the pragmatist are plainly designed of solid colors, the true fashion plate will no doubt want to take his pick of thousands of designs, such as a flames, skulls, flaming skulls, camouflage, celtic crosses, and the like. They are cheaply (expect around U.S. $5-10 retail) and easily available at thousands of head shops, biker stores, and urban apparel outlets across the country.
Sadly, this innocuous, highly useful piece of clothing has come under quite a bit of scrutiny in the last few decades, and also developed an overall negative connotation in middle-class culture (which may very well be inversely related to its tremendous appeal to the common man). Wearing a colored dew rag, or bandana in general -- whether it be worn about the head in the normal fashion or anywhere else on the body -- is regarded by many as a flagrant, if unintentional, gesture of gang affiliation, specifically with one whose members tend to favor its color as an identifying mark. This has compelled most American schools to ban 'rags in general as an inappropriate form of attire and enthusiasts to curtail or eschew their usage in some urban environments, particularly those with a higher-than-average crime rate.
Fortunately, in spite of this minor setback, dew rags are well-poised to carry on strong into the new millennium. They are affordable, comfortable, evocative, and quite possibly the only form of 17th-century pirate fashion that is not considered effeminate in modern 21st century culture.