Act 3, scene 2 of John Webster's The Duchess of Malfi shows the duchess being inconveniently visited by her brother and nemesis Ferdinand. Ferdinand is angry because rumors have reached him that his sister, a widow, has taken a lover or even a husband—who the audience knows to be Antonio.

Ferdinand is angry because he fears that his sister's actions will tarnish their family name and reputation. Also, a new husband for the duchess would mean that she would have a guardian for her wealth, which Ferdinand covets. Most importantly, it is implied that Ferdinand has an unnatural and unhealthy attraction toward his twin sister, the duchess, and that the possibility of her having a man makes him jealous.

During this surprise visit, Ferdinand argues with the duchess about her current status and makes threats to whoever is the man who is "enjoying" his sister. In his monologue, Ferdinand goes into a diatribe about how he is ready to unveil the secret and how the duchess is supposed to behave. To this, he adds,

Do not keep a paraquito, lest she learn it;
If thou do love him, cut out thine own tongue
Lest it bewray him.

A paraquito, or a parrot, is likely to repeat the name of this yet-unnamed man in the life of the duchess, he says. Ferdinand is telling the duchess that the parrot may give away the identity of her new man, so he is sarcastically warning her from keeping one of these birds.