It's pretty much a given that no rapper actually goes by their real name; it's just not the done thing within that genre of music. Wiz Khalifa probably could have though, his real moniker is Cameron Jibril Thomaz. Apparently, his last name really is spelled with the 'z' at the end, which marks it out as pretty distinctive on its own, so where did his stage name come from?
The answer is typically modest! According to the man himself, his first rap name was 'Young Wiz', because he was good at everything he did. It must be fantastic to have that kind of confidence. The second part, 'Khalifa', is an Arabic word meaning 'successor', so you could roughly translate his stage name as 'Great Successor'. That's quite the statement of intent. We can't argue with it though; his success to date more than backs it up.