You mean Fleur-de-lis. This is a heraldic symbol made up of three petals.
See
http://www.fleurdelis.com/fleur.htm
It was used by the kings of
France in their coats-of-arms.
In "The Three Musketeers" (Alexendre Dumas), Milady de
Winter has a fleur-de-lis branded on her left shoulder because she was a murderess. Whether or not this was standard practice in
France for marking the worst criminals, I don't know.