The preserved records of the Reichssicherheitshauptamt (Reich Security Main Office) show the persecution of the Freemasons. While the number is not accurately known, it is estimated that between 80,000 and 200,000 Freemasons were exterminated under the Nazi regime.
In 1926, the little blue Forget Me Not was first used by the Grand Lodge Zur Sonne as a Masonic emblem at the Annual Convention in Bremen. Then in 1934, the Nazis introduced the Winterhilfswerk, a supposed charitable organization, which actually collected money used for rearmament. The contributors received a badge that changed each winter. In March 1938 the Forget Me Not badge - made by the same factory as the Masonic badge - was chosen, enabling Freemasons to wear it as a secret sign of membership.
After the Second World War, the Forget Me Not flower was used again as a Masonic emblem at the first Annual Convention in 1948 of the United Grand Lodges of Germany, Ancient Free & Accepted Masons. The badge is now worn in the coat lapel by Freemasons around the world to remember all those that have suffered in the name of Freemasonry, and specifically those during the Nazi era.
-- from Wikepedia