Crackin means happening. Adding some kind of word that gives the word a sense of action - like a spinning wheel....something that is in a state of action ; you can say: what's crackalatin ? and this actually means "yo / hey, what’s happening ?!"

crack-a-latin - a person who does two impossible things at once, like smoking crack and speaking perfect latin.

Eminem uses it in the D12 CD.

Used to express what a "cracker" is doing at that time