(Tony - originally from NSW & Qld folkscenes - has also remembered that he probably first encountered the term in Darwin, about 1982 ...)
I also seem to recall a Darwin variant that used ".... Groaned Euphoniously" in its derivation!!! This, however, is somewhat at odds with my partner - Lawls'- memory. He reckons everyone who could still stand at the end of the night, got on the stage and "sang" - and the results were often not the prettiest!!!!!