Hath Romeo slain himself? say thou but "I,"
And that bare vowel "I" shall poison more
Than the death-darting eye of cockatrice.
– William Shakespeare
Romeo and Juliet, Act 3, Scene 2. Juliet tells her Nurse that if Romeo has killed himself that will be more poisonous to her than the deadly gaze of a cockatrice. This is a mythical beast with two legs, wings and a rooster’s head, whose looks could kill. Juliet puns on "I" and "eye" – the affirmative particle "ay," meaning yes, was commonly written "I" in Shakespeare’s time.