Short for "What are you doing now?"
BACKROUND INFORMATION:
Doni was a mistake made in an
AIM conversation. Instead of asking "What are you doing?", the person decided to shorted it to "Doin?". But, they happened to make a mistake and type "Doni?". From that point forward they coined the phrase "Doni?", not ony becasue they were
otaku and it sounded japanese, but just because it sounded
cool.