Two-piece garments worn by women for athletic purposes have been observed on Greek urns and paintings, dated as early as 1400 BC.
Sometimes the term bikini is used to describe the type of man's swimsuit also known as speedoes
the modern bikini was invented by French engineer Louis Réard and fashion designer Jacques Heim in Paris in 1946 and introduced on July 5 at a fashion show at Piscine Molitor in Paris. It was a string bikini with a g-string back. It was named after Bikini Atoll, the site of nuclear weapon tests a few days earlier in the Marshall Islands, on the reasoning that the burst of excitement it would cause would be like the nuclear device.
Reard's suit was a refinement of the work of Jacques Heim who, two months earlier, had introduced the "Atome" (named for its size) and advertised it as the world's "smallest bathing suit". Reard 'split the "atome"' even smaller, but could not find a model who would dare to wear his design. He ended up hiring Micheline Bernardini, a nude dancer from the Casino de Paris as his model. .
Bikini-style swimwear existed for many years befor the first official bikini, however. The July 9, 1945, issue of Life, for example, shows women in Paris wearing similar items. Films of holidaymakers in Germany in the 1930s show women wearing two-piece bathing suits. Anyone who has seen the elaborately and lavishly assembled Busby Berkeley film spectacle, Footlight Parade of 1932 (with James Cagney, Dick Powell, Ruby Keeler, Joan Blondell, etc.), would have been treated to a stunning aquachoreography that profusely featured what could only be regarded as bikini swimwear. They were to be seen again a year later in Gold Diggers of 1933.
In 1951 bikinis were banned from the Miss World Contest following the crowning of Miss Sweden in a bikini and subsequent protests with a number of countries threatening to withdraw. In 1957, however, Brigitte Bardot's bikini in And God Created Woman created a market for the swimwear in the US, and in 1960, Brian Hyland's pop song "Itsy Bitsy Teenie Weenie Yellow Polka Dot Bikini" inspired a bikini-buying spree . In 1962, an icon was born as Bond Girl Ursula Andress emerged from the sea wearing a white bikini in Dr. No. Finally the bikini caught on, and by 1963, the movie Beach Party, starring Annette Funicello (emphatically not in a bikini, by mentor Walt Disney's personal request) and Frankie Avalon, led a wave of films that made the bikini a pop-culture symbol.
In Malta, bikinis took time to be introduced. In the 1960s, the police fended off Bishop Michael Gonzi's request to ban bikini clad tourists following fear of compromising Malta as a tourist destination. Malta Labour Party girls felt safe putting on bikinis during beach parties but this was unacceptable by those supporting the Nationalist Party.
Source : http://en.wikipedia.org/wiki/Bikini