Yo- where did it come from? What does it mean?

According to the Urban Dictionary Yo means:
1) A contraction of the possessive prenominal adjective “your.”
2) An informal address or title to one whose name is not known to another; can be used as an interrogative address.
3)A declaritive or imperative exclaimation, whether alone or within a sentence.
1) How’s yo momma?
2) Hey, yo! What’s up, yo?
3) Yo! What the hell do you think you are doing?! Yo, just do your job! YO!

Who really cares… you want facts Rocky Balboa was the one to make this word blowup. Am i wrong?

inspired by @phillian