E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Marguerite des Marguerites [the pearl of pearls].
So François called his sister (Marguerite de Valois), authoress of the Heptameron. She married twice: first, the Duc dAlençon, and then Henri dAlbret, king of Navarre, and was the mother of Henry IV. of France. Henri [IV.] married a Marguerite, but this Marguerite was the daughter of Henri II. and Catherine de Medicis. The former befriended the Huguenots, the latter was a rigid Catholic, like her mother.