Romeo and Juliet, Act 2, Scene 2
This is one of Shakespeare’s best known lines – from Romeo and Juliet, 1592.
‘The ‘wherefore’ here means why rather than where. Juliet makes her speech from the balcony while Romeo stands unseen in the shadows beneath.
What Juliet is asking, in allusion to the feud between her Capulet family and Romeo’s Montague clan, is ‘Romeo, why are you a Montague?’. Their love is impossible because of their family names and she asks him to change his allegiance, or else she will change hers.