The word bikini has surprisingly radioactive origins. The English word came from French, since the French invented the bikini, and the French word came from an English name for a Pacific atoll that was the site of several nuclear tests. this is kind of a joke: the bikini was where the US "split the atom", and an atome was a single-piece French bathing suit. Anyway, the bikini part of bikini atoll came from the Marshallese appellation pikini. This is likely a combination of pik, meaning "surface" and ni, meaning "coconut". Further research on this is hard to find, because etymologists favor Indo-European languages over supposedly insignificant native tongues, but this probably came from the Proto-Micronesian language, which in turn comes from Proto-Austronesian. Funnily enough, the bi- part of bikini was later on mistaken for a prefix, and caused the creations of the words monokini and trikini.
Adam Aleksic, a leading contender for valedictorian of his high school, is a 210-month-old boy with disturbing interests in etymology, vexillology, geography, and law. Adam would like to one day visit Tajikistan and probably isn't spying for the Kyrgyz government.
The Etymology Nerd