A popular greeting widely considered to have originated in the underground East coast rap scene. Credited in it's earliest uses to rappers Queue and Illustrious C of the Hip Hop group Legion of Doom. A combination of 'Yo' and 'Hi', it rhymes with the latter.
"Yi muthafucka, time to pull out my nine. 'Gonna slap a couple bitches fo' I guzzle some wine." ~From the track 'Upscale Anal' as featured on the Legion of Doom album 'Jockstrap in my Martini'.