The forget me not flower has been associated with Freemasonry since WW II. Freemasonry was outlawed by the Nazi Party in Germany and the occupied areas. Freemasons were hunted down and send to concentration camps during the holocaust. The number of Freemasons who were killed range from 60,000 to 250,000. The real number will unfortunately never be known.
In 1938 a factory in Bremen, Germany produced a blue forget-me-not lapel pin on behalf of the National Socialist People’s Welfare Organization, to commemorate its Winterhilfswerk, or winter charitable contribution drive. The pin was a gift to its donors. According to legend Freemasons wore the forget-me-not flower as a lapel pin instead of the traditional square and compasses to secretly identify each other during these times of persecution.
In 1948 at the first convent of the United Grand Lodges of Germany, the flower was officially adopted as a way to remember their fallen brethren. Later on in 1948 when then Grand Master of the Grand Lodge of Germany AF&AM, Theodor Vogel, attended the Grand Masters conference in Washington DC, he distributed these pins and first told the story to Masons outside of Germany.
Since then the idea that it would have been possible for Freemasons to so openly defy the Nazi party for so many years has come under contention. Nevertheless, regardless of how accurate the story is, using such an aptly named flower reminds us of the fidelity and resilience that Freemasons display to this day while being suppressed, harassed and even persecuted.
More Info:
https://grandlodgeofiowa.org/docs/Philosophy_Masonry/ForgotMeNot.pdf
http://www.masonrytoday.com/index.php?new_month=03&new_day=26&new_year=2018
http://www.masonicnetwork.org/blog/2009/the-story-behind-forget-me-not-emblem/