Long johns, also known as long underwear, thermal underwear or pajamas, are two-piece garments worn underneath clothing to provide an extra layer of warmth. Either men or women may wear them at night as pajamas, and children’s pajamas may imitate the long johns style. Though first made in wool or rough cotton, long johns are now made in a variety of fabrics. Some new fabrics are particularly designed to resist water or to help wick perspiration away from the body so as not to make a person too warm or soaked by sweat.

Long underwear, up through the early 20th century, were normally one-piece constructions. They might feature a “backdoor” which made bathroom trips a little easier. The ability to pull the pants part of long johns down from the waist was a far more convenient element, making them preferable over one-piece long underwear.

Frank Stanfield, a Nova Scotian, is credited with the invention of long johns in 1915. In fact Stanfield's continues to make long johns today, combining more modern fabrics and styles with this first design. Though at first only popular in Canada, long johns began to grow in popularity in the United States, so much so that they became part of army standard issue in World War II for those fighting in the trenches or in any type of ground engagement. Stanfield’s early version of long johns, and those issued in the US to armed forces were typically wool and often itchy.

How two-piece long underwear began to be called long johns is rather a mystery. Some people believe that the John in long johns refers to John L. Sullivan, a boxer, who frequently wore long john bottoms, or long drawers tucked into his socks and shoes. This theory on the naming of long johns has not been proven, but seems the most viable explanation for name origin.

As a clothing layer, long johns are worn by many in cold climates, or in climates with harsh winters. The layer effect provided by them does certainly add to warmth. If you’re looking for natural fabrics that are light, silk long johns are often preferable, though some complain they feel too warm. Acrylic and polypropylene may be preferred fabrics. Some long johns in cotton have a waffle weave fabric that is often considered “thermal fabric.” If the cotton or other materials used are soft, waffle weaves can be comfortable. Inferior fabrics may make these itchy and uncomfortable, and they may shrink easily.