Bikinis were named after Bikini Atoll, the nuclear weapons tests site

According to Wikipedia, “a swimsuit, bathing suit, togs or swimming costume is an item of clothing designed to be worn while participating in water sports and activities such as swimming, water polo, diving, surfing, water skiing, or for any activity in the sun, such as sun bathing. It is also used as an undergarment in sports that require a wetsuit such as waterskiing, scuba diving, surfing, and wakeboarding. In New Zealand English and some areas of Australian English, swimsuits are usually called togs or bathers. The term, togs, is less common in other parts of the Commonwealth, where it can also refer to clothes in general.”

The history of swimsuit and similar clothing with descriptions as above makes interesting reading, if not funny and entertaining. In the ancient times swimming and bathing were mostly without wearing any clothing, but in some cases curtains or coverings were used to restrict view to the public.

About 2000 years old murals found at Pompeii, a ruined and partially buried ancient Roman town near modern Naples in the Italian region of Campania, show women wearing two-piece suits, remarkably similar to a bikini of 1960s. But after this, such bathing apparel seems to have been lost for centuries.

Bikini historians are of the view that with the invention of the railways, and the popularity of rail travel in the mid 1800s, it became possible for large number of people to visit beaches. So, in the 18th century women wore ‘bathing gowns’ in while in water. These were long dresses, which would not become transparent when wet, with weights sewn into the hems so that they would not rise up in the water and show women’s bodies. The men's swimsuit, a form-fitting garment with long sleeves and legs similar to long underwear, became popular and its body coverage remained the same for a century.

In the 19th century, woman's two piece swimsuit, a gown from shoulder to knees plus a set of trousers with leggings going down to the ankles, became common. In the Victorian era, popular beach resorts were commonly equipped with bathing machines designed to avoid the exposure of people in swimsuits, especially to people of the opposite sex.

In 1907 the swimmer Annette Kellerman from Australia visited the United States as an ‘underwater ballerina’, a version of synchronized swimming involving diving into glass tanks. But she was arrested on charges of indecent exposure because her swimsuit exposed her arms, legs and neck. Then Kellerman modified her suit with long arms and legs and a collar, but keeping the tight fit that revealed her shapes underneath. She later starred in many movies, including one about her own life.

After this, thanks to Annette Kellerman, bathing wear started to shrink, first exposing the arms, and then the legs up to mid-thigh. Collars receded from around the neck down to around the top of the bosom. The invention of new fabrics allowed for new varieties of more comfortable and practical swimwear.

Due to the figure-hugging nature of these garments, glamour photography in the 1940s and 1950s often featured people wearing swimsuits. This eventually evolved into swimsuit photography, as exemplified by the Sports Illustrated annual swimsuit issues.

The first bikinis were introduced just after World War II. Early bikini designs were not very different from women's two-piece bikinis of 1920s, except that they had a gap below the breast line allowing for a section of bare midriff. Bikinis were named after Bikini Atoll, the site of several nuclear weapons tests, for the bikinis’ explosive effect on the viewer.

In the 1950s, it was proper for the lower part of the bikini to come up high enough to cover the navel. But from 1960s, the bikini shrank in all directions until it covered the bare minimum of body. Around this time, fashion designer Rudi Gernreich introduced the monokini, a topless swimsuit for women consisting of a modest bottom supported by two thin straps. It was not a commercial success, but it opened up new design possibilities. In the 1980s the thong or ‘tanga’ entered the fashion scene from Brazil, possibly inspired by the traditional garments of native tribes in the Amazon.

Men's swimsuits evolved along with women's swimsuits during this period, with the shorts covering less of the body. Then the racing-style ‘speedo’ suits became popular. Thongs, G-strings, and bikini style swimsuits were also in vogue, more popularly in tropical regions.