1958, proprietary name (Britain), from French vel(ours) cro(ché) "hooked velvet."
Here is a nonmetallic fastener with no mechanical parts. It is simply two strips of nylon, one woven with thousands of tiny protruding hooks, the other with loops. Pressed together, they catch like a burr to clothing, can't be parted except by peeling. American Velcro, Manchester, N.H., makes them to hold anything from pants to upholstery. [Popular Science, December 1958]
"low-waisted two-piece women's bathing suit," 1948, from French, coined 1947, named for the U.S. A-bomb test of June 1946 on Bikini, the Marshall Islands atoll, locally Pikinni and said to derive from pik "surface" and ni "coconut," but this is uncertain. Various explanations for the swimsuit name have been suggested, none convincingly, the best being an analogy of the explosive force of the bomb and the impact of the bathing suit style on men's libidos (compare c. 1900 British slang assassin "an ornamental bow worn on the female breast," so called because it was very "killing," also the figurative sense of bombshell).
Bikini, ce mot cinglant comme l'explosion même ... correspondant au niveau du vêtement de plage à on anéantissement de la surface vêtue; à une minimisation extrême de la pudeur. [Le Monde Illustré, August 1947]
As a style of scanty briefs, from 1960. Variant trikini (1967), with separate bra cups held on by Velcro, falsely presumes a compound in bi-.