The best-known story about the word nylon is that it joins NY, for New York, and LON, for London. It is a neat story, and it is false.
Snopes calls it "neat pop etymology" and points out that London played no part in nylon's history. The fiber was an American DuPont product from start to finish. Another story says the letters stand for "Now You've Lost, Old Nippon," a jab at Japan's silk trade. Snopes calls that spurious too.
The real story is a committee and a lot of rejected names. Wallace Carothers's team at DuPont made the polymer in 1935. The Science History Institute says researchers called it Rayon 66, Fiber 66 or "Duparon." Snopes reports that DuPont weighed about 400 names, including "Duparooh," for "DuPont Pulls A Rabbit Out Of Hat."
How the committee got to nylon is less clear. The Science History Institute calls the process "somewhat obscure." In the account it quotes from DuPont's Ernest Gladding, the first choice was "Nuron," which spelled "no run" backward. Nuron and similar words posed trademark conflicts, so the division proposed "Nilon." Changing the "i" to a "y" settled the pronunciation.
Wikipedia cites a 1978 DuPont publication that tells it slightly differently. There the starting point was "No-Run," a promise that stockings would not ladder. The stockings were not truly run-proof, so the name was reworked through "nuron" and "nilon." Either way, "no run" sits somewhere in nylon's past.
DuPont's official explanation of the finished word is plainer. Etymonline says the company described "nyl" as a random syllable. Wikipedia quotes a 1940 statement by DuPont's John W. Eckelberry that the "-on" was copied from fibers such as cotton and rayon.
The word appeared in 1938, when DuPont announced the fiber. Snopes notes that nylon stockings debuted at the New York World's Fair, and Etymonline dates "nylons," meaning the stockings, to 1940.
The "-on" ending kept working for DuPont. Etymonline says Orlon (1948) and Dacron (1951) were also invented names, and that Dacron was modeled on nylon. None of them is an acronym, and neither is nylon.