Welcome ABoard, mike. If you wish to shrive yourself of your guilt, I might suggest visiting this message board: <http://pub122.ezboard.com/bwordoriginsorg>

Don't put forth your claim of inventing it, just ask after the origin.

FWIW, my JunkDrawerMemory® has a faded note in it suggesting that "heavy metal" was a translation of a French graphic novel genre better translated as "screaming metal". The date on the note, if I can read it aright, is in the early '60s.