In the years between WW1 and WW2 the blue forget-me-not was a standard symbol used by most charitable organizations in Germany, with a very clear meaning: "Do not forget the poor and the destitute". It was first
introduced in German Masonry in 1926, well before the Nazi era, at the annual Communication of the Grand Lodge "Zur Sonne", in Bremen, where it was distributed to all the participants. That was a terrible time in
Germany, economically speaking, further aggravated in 1929 following that year's "Great Depression". That economic situation, by the way, contributed a lot to Hitler's accession to power. Very many people depended on charity, some of which was Masonic. Distributing the forget-me-not at the Grand Lodge Communication was meant to remind German Brethren of the charitable activities of the Grand Lodge.
In 1936 (Hitler was already in control since 1933) the "Winterhilfswerk" (a non- Masonic winter charity drive) held a collection and used and distributed the same symbol, again with its obvious charitable connotation. Some of the Masons who remembered the 1926 Communication --and the forget-me-not-- possibly also wore it later as a sign of recognition. We have no evidence of that and its general signification still was charity, but not specifically Masonic charity. Moreover it rapidly became quite impossible to risk wearing anything but Nazi pins. So there were probably only a very few Brethren wearing the forget-me-not, and probably only for a
brief time, until wearing any non-Nazi pins became suspect. There is absolutely no record of the pin, or the flower, ever having been worn during the war (that is after 1939), even less in concentration camps, as the legend also goes.
In 1948 Bro. Theodor Vogel, Master of the Lodge "Zum weißen Gold am Kornberg", in Selb (then in Western-occupied Germany), remembered the 1926 and 1936 pin, had a few hundred made and started handing it out as a Masonic symbol wherever he went. When Brother Vogel was later elected GM of the Grand Lodge AFuAM of Germany and visited a Grand Masters' conference in Washington, DC, he distributed it there too, and this was the way it first came to the USA.
Its sudden popularity caused many manufacturers, some Masonic, some not, to pounce upon the occasion and sell the pin all over the world, with a variety of rather contrived and imaginative notes of explanation. The pin is nowadays quite well-known, as are the legends written about its origin, purpose and use... Which does not deter after all from the new message it carries today, through its authors' imagination if not through rigorous historical record...
And since we are mentioning the forget-me-not, it is any of about 50-odd species of the genus Myosotis, family Boraginaceae, carrying clusters of blue flowers and native to temperate Europe, Asia and North America.