Brewer's: Forbidden Fruit
(The), Mahometan doctors aver, was the banana or Indian fig, because fig-leaves were employed to cover the disobedient pair when they felt shame as the result of sin. Called ?Paradisaica.? Metaphorically, unlawful = forbidden indulgence.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894