The modern two-piece swimsuit, invented by Louis Réard in 1947, was named after Bikini Atoll, an island in the Pacific that was being used to test an atomic bomb in 1946.
Réard wanted to make the connection: he compared the "burst" of excitement that would come from the new swimwear option to that of the bomb. (He clearly left the devastating after-effects of the nuclear weapon out of the advertisements!)
Also, conveniently for the metaphor, another French designer, Jacques Heim (a competitor of Réard's), had invented a small women's bathing suit called the "Atome" (since it was "so tiny"). Since Réard's bikini was basically a two-piece version of Heim's design, he said that he "split the Atome", much like the atomic bomb splits atoms.
Wow. Part clever and part crazy!