Wherefore means "Why".
So when Juliet says "Wherefore art thou Romeo"
She's saying "Why are you Romeo?"
"Wherefore" means "why" or "for what reason." It is often used in a more formal or poetic context to ask about the reason or purpose behind something.
accordingly, consequently, ergo, therefore, so, thereupon, thus, wherefore
The wherefore clause is where you ask the court for the relief you are seeking.
I disagree with the popular answer of it meaning "why" in this usage. That meaning doesn't make much sense since it was his surname that was the subject of the passage. The word, "wherefore" can also mean "where". This does make sense as she didn't have to go to an open window to make her statement or soliloquy. Her calling out, "Wherefore art thou" meant that she didn't know he was present and it supports her statement "What man art thou, that, thus be-screen'd in night, So stumblest on my counsel?" as he was obscured in the darkness below.
Repetition
Wherefore means why. "Wherefore art thou Romeo?" means "Why are you Romeo?" Juliet is asking why he is Romeo, or more simply why does he have to be a member of the Montague family.
Why. Or wherefore. Your choice. Shakespeare used both, frequently in the same sentence. e.g. Say, wherefore didst thou lock me forth to-day? And why dost thou deny the bag of gold? (Comedy of Errors, 4,4) Say, why is this? wherefore? What should we do? (Hamlet, 1,4) Why bastard? wherefore base? (King Lear, 1,2)
synonyms for why: wherefore how come
There is an old Warner Brothers cartoon about an amateur hour type competition in which a couple does the balcony scene--misunderstanding the meaning of the word "wherefore" of course.
y wherefore also means why
Whether is used to raise question where you have to choose from two given options i.e. whether you like to have coffee or tea. Wherefore is an obsolete word which was used as "why" in old English.
wheelback, waterbird, wherefore
Marjorie Armstrong has written: 'The why and wherefore'