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Long underwear, also called long johns or thermal underwear, is a style of two-piece underwear with long legs and long sleeves that is normally worn during cold weather. It is commonly worn by people under their clothes in cold countries.
In the United States, it is usually made from a cotton or cotton-polyester-blend fabric with a box-weave texture, although some varieties are also made from flannel, particularly the union suit, while many newer varieties are made from polyester, such as the Capilene trade name.
European manufacturers use wool blends or even 100% wool, usually Merino or other high-quality wool. Some models might include a thin layer of polyester to transport moisture away from the skin. Wool, in addition to being fire retardant, provides highly effective insulation and will keep its insulating properties even when wet, as opposed to cotton.
The type known as "thermal underwear" is made from two-ply fabric of either a wool layer and an artificial fibre, only wool or – again mostly in the U.S. – two layers of only artificial fibres, which uses trapped body heat to insulate against cold air.
Etymology of "long johns"
The manufacturing foundations of long johns may lie in Derbyshire, England, at John Smedley's Lea Mills, located in Matlock. The company has a 225-year heritage and is said to have created the garment, reputedly named after the late-19th-century heavyweight boxer John L. Sullivan; the company still produces long johns.
In 2004, Michael Quinion, a British etymologist and writer, postulated that the "john" in the item of apparel may be a reference to Sullivan, who wore a similar-looking garment in the ring. This explanation, however, is uncertain and the term's origin is ultimately unknown. So it is also very probable that it's simply a deformation of "longues jambes" meaning "long leg" in French.
History of long johns
Long johns were first introduced into England in the 17th century, but they did not become popular as sleepwear until the 18th century. They were supposedly called long johns after a famous knife fighter who fought in long underwear. They were first used as loungewear but then later became popular as sleepwear. Children also wore long johns as sleepwear, usually made out of cotton and polyester.
An adjustable two-piece design is credited to Myles Stanfield, a native of Truro, Nova Scotia, who patented his design on 7 December 1915. In 1898, Myles and his brother John had developed a product called Stanfield's Unshrinkable Underwear for Stanfield's, their garment manufacturing company.