Thou know’st the mask of night is on my face,
Else would a maiden blush bepaint my cheek
For that which thou hast heard me speak to-night.
– William Shakespeare
Romeo and Juliet, Act 2, Scene 2. Juliet is embarrassed when she realizes that Romeo was listening to her while she was thinking out loud on her balcony. Her blushes are saved by the dark, she says, using the metaphor of mask for night.