The mishearing/mispronounciation of the Warcraft 3 Footmen dialogue "What do you need?"
Commonly used as a prefix to a scentence, in replacement of reply, acknowledgement among friends or called out randomly without context.
Person A - "Just heading down to the shops, Ey Boi Didi"
Person A - "Hey man, how's it going?"
Person B - "Ey Boi Didi"
Person A - "Ey Boi Didi"
Person B - "Ey Boi Didi"