Used in a first person tense when addressing someone when you don't know their name, or using it instead of 'Dude'. A derivation of the phrase 'yo man', but the trailing twangy g was added for those times when you know the name of the person you are talking to, but address them indirectly.
"Yomaing, do you have any plans for tonight?"
"Hey Yo maing... do you have a light?" - <note to prefix Yo with the icebreaker hey, and add the 'maing' separately to get the attention of the listener>