Possibly a combination of what up with how goes it and similar phrases.
what it is?
- (slang, African American Vernacular English) A casual greeting
1997, April Sinclair, Ain't Gonna be the Same Fool Twice, HarperCollins, →ISBN, page 181:
"What it is?" David greeted me.
2001, Chris Fuhrman, The Dangerous Lives of Altar Boys, University of Georgia Press, →ISBN, page 162:
A boy broke out of the crowd shouting, "Hey! Hey! What it is, brothers, what it is?"
2007, K'wan, Still Hood, Macmillan, →ISBN, page 87:
"What it is, my niggaz?" Hollywood gave True a pound then jerked him in for a hug.