E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Vanessa
is Miss Esther Vanhomrigh, and Cadenus is Dean Swift. While he was still married to Stella [Miss Hester Johnson, whose tutor he had been] Miss Vanhomrigh fell in love with him, and requested him to marry her, but the dean refused. The proposal became known to his wife (?), and both the ladies died soon afterwards. Hester Johnson was called Stella by a pun upon the Greek aster, which resembles Hester in sound, and means a star. Miss Vanhomrigh was called Van-essa by compounding Van, the first syllable of her name, with Essa, the pet form of Esther. Cadenus is simply decanus (dean) slightly transposed.