Grab one of the overhead straps, folks, because this train is veering wildly off-topic!
I'm back at work now where I have access to the Oxford English Dictionary. It lists two entries for "hoon".
The first is of Indian origin, derived from the Hindi word "huna", and is alternatively spelled "hun". The word refers to a particular denomination of gold coin, and was primarily used in the 1800's.
The second definition is the one we're looking for. It's listed as being "Australian slang", and is defined as "A lout, a rough; a crazy person, a ‘clot’; a ponce." The earliest citation is from 1938. By 1969, the word was linked to racing cars (the citation mentions "hot-rod hoons").
Unfortunately, the OED lists the etymology as "origin unknown". I wonder, however, if it might be an alteration of "goon". Not in the "idiot" sense, but in the "hired thug" sense. The earliest citation the OED shows for that meaning is, coincidentally, also 1938.