The Duchess of Portsmouth, a favourite court lady of Charles II. The allusion is to the wife of Uriah the Hittite, criminally beloved by David (2 Sam. xi.). The Duke of Monmouth says:
My father, whom with reverence yet 1 name, Charmed into ease, is careless of his fame; And, bribed with petty sums of foreign gold, Is grown in Bathsheba's embraces old.
Dryden: Absalom and Achitophel, i. 707-10.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
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