Brewer's: Saccharissa

A name bestowed by Waller on Lady Dorothea Sidney, eldest daughter of the Earl of Leicester, for whose hand he was an unsuccessful suitor, for she married the Earl of Sunderland.

“The Earl of Leicester, father of Algernon Sidney, the patriot, and of Waller's Saccharissa built for himself a stately house at the north corner of a square plot of `Lammas land' belonging to the parish of St. Martin's, which plot henceforth became known to Londoners as `Leicester Fields.' ” —Cassell's Magazine: London Legends, ii.

Saccharissa turns to Joan

(Fenton: The Platonic Spell). The gloss of novelty being gone, that which was once thought unparalleled proves only ordinary. Fenton says before marriage many a woman seems a Saccharissa, faultless in make and wit, but scarcely is “half Hymen's taper wasted” when the “spell is dissolved,” and “Saccharissa turns to Joan.”

Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894

Sacco Benedetto

Saccharine Principle in Things