YOWZA

In common use in advertising and on the net, often in same sense as Wow! or Yeah! For some reason in a number of web ads regarding cross country biking. Try doing a deep search on the web to find this word. I've looked for days with no joy. Thought it might be from southern minstrel days--exaggerated slave speak. Does anyone actually have a reference or etymology on this real expression? Thanks. Example: Yowza! New Cross country race will be awesome.