What does it mean? Do you know?
Here is one theory
http://www.heraldica.org/topics/fdl.htm
***Etymology: Middle English flourdelis, from Anglo-French flur de lis, literally, lily flower
1 : IRIS 3
2 : a conventionalized iris in artistic design and heraldry
[fleur-de-lis illustration]***
I'm not Snugs, but I'm answering because I've always loved that design, especially in its more simple form.