From Tolkien Gateway

Evermind was a translation of the name simbelmynë, the name in Rohan for the small white flower that grew especially on the graves of Men. This association with the dead was the source of the flower's name - 'everlasting memory'.


Tolkien noted that the element -mind has the sense "memory". Although the name resembles "forget-me-not" it's not the same kind of flower.[1]