WSS Character Analysis Questions...

Been lookin all over the place for some character breakdown/analysis for West Side Story. Specifically for the Jets.
Even more specifically, why are they named what they are named?

Baby John for instance is pretty obvious..
Diesel is obvious too...

but what about A-Rab? Anyone know why they call him that?

The only thing I can find is this

* Tony/Romeo
* Maria/Juliet
* Chino/Paris
* Bernardo/Tybalt/Lord Capulet
* Riff/Mercutio/Lord Montague
* Baby John/Benvolio
* Anita/Nurse
* Doc/Friar Lawrence/Balthasar
* Schrank/Prince Escalus
* Krupke/Peter
* A-Rab/Abraham
* Jets/Montagues
* Sharks/Capulets

That Abraham is his Romeo and Juliet counterpart...anyone?

Thanks for the help

If you can't help then don't reply with snide remarks. I started off by saying "Been lookin all over the place" therefore I HAVE been doing homework.