Wha gwaanin is a hybridised British version of "wha (whaa) gwaan." Wha gwaan is an enquiry of the general state of events in your life (or just a friendly greeting). Wha Gwaanin is more like asking "whats going on with you right now."
"Wha gwaan mi bredren?" - "How are you getting on my brother/friend"
"Wha gwaanin mi bredren?" - "What is going on (currently) my brother/friend"
"Wha gwaanin mi bredren?" - "What is going on (currently) my brother/friend"
by Bamboodread February 23, 2016