Swedish-American engineer Gideon Sundback finally cracked the code by adding more teeth and a working slider. However, nobody called it a "zipper" yet—that name came in 1923 when a rubber boot company used it and loved the "zip" sound it made. Why "Fly"?
Elias Howe, the man who patented the sewing machine, actually patented the first clothing closure. However, he was so busy with his sewing machine that he left the idea to collect dust for decades. Fly zip
The story of the "fly zip"—or fly-front zipper—is a tale of accidental inventions, persistent failure, and a final "zip" that changed fashion forever. The 80-Year Struggle Fly zip