I don't think there's a connection. 'West Side Story' has its own established story and characters, and 'A Rab' doesn't seem to fit into that framework. It could be a random combination or a misunderstanding.
There might be no connection at all. 'West Side Story' is a well-known musical, while 'A Rab' could be something very specific or less-known, and it's not clear how they would be related. Maybe it's a reference to a very niche aspect that most people aren't familiar with.