Niece of Sir Toby Belch. Malvolio is her steward, Maria her
woman, Fabian and a clown her male servants. (Shakespeare: Twelfth
A female Tartuffe (q.v.)
in Wycherley's Plain Dealer
. A consummate hypocrite, of most unblushing effrontery.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894