Wikipedia
Winny (also known as WinNY) is a Japanese peer-to-peer (P2P) file-sharing program which claims to be loosely inspired by the design principles behind the Freenet network, which makes user identities untraceable. While Freenet was implemented in Java, Winny was implemented as a Windows C++ application.
The software takes its name from WinMX, where the M and the X are each advanced one letter in the Latin alphabet, to N and Y. According to a 2006 report by the Recording Industry Association of Japan, more than three million people had tried Winny.
Like Freenet, each client functions as a node. Initially, a search returns few results, but one can set up "clusters" based on certain keywords, and over time, one's client will learn the best route to obtain the information sought.
The software was developed by Isamu Kaneko, who was a research assistant in graduate course of computer engineering at the University of Tokyo in Japan. He was also once a researcher at the Japan Atomic Energy Research Institute. Kaneko originally anonymously announced his intent of developing the software on the Download Software board of the popular 2channel ( 2ch for short) Japanese bulletin board site. Since 2ch users often refer to anonymous users by their post numbers, Kaneko came to be known as "Mr. 47" ("47-Shi", or 47氏 in Japanese), or just "47". Kaneko died on the 6 July 2013 after suffering a heart attack.
After Winny's development stopped, a new peer-to-peer application, Share, was developed by an anonymous Japanese engineer to replace Winny.