Person associated with an activity--for example, god wallah for priest
"Dude" in chatroomese. It's an Indian greeting, but over at "Arab Chat" it just seems to mean, well, "Dude."
By Allah (Arabic: Wallah) is Arabic expression meaning "[I promise] by God" used to make a promise or express great credibility on an expression. It is considered a sin among Muslim to use this phrase and follow it up with a lie. Also, some Muslims argue that this is one of the few valid ways of making a promise, the variant "I promise on myself" or "I promise on my own soul" not being allowed, in contrast to "I promise by the one who holds my soul" ie God.