Yep. Nang is the best word bar none. Basically there was this Filipino girl called Nang Phen who was fit. Thus the word nang came to represent anything that was cool/amazing. Only word that's been mentioned on this thread that I as a lad from Cardiff would feel like a dick saying. Way too East London for me to get away with.
I like that story, tho' not heard the word before. The one I'm interested in is 'cotch' which is used within the black community. I'm sure it comes from the Welsh word 'cwtch', which itself could have come from 'coucher' in French, which is to lie down, go to bed. My nana always to say, "there, there, cwtch up now" if we were upset or tired.