Now, Bogie, it takes a real sophisticate to be familiar with this term. A man of letters.Great googly moogly!
I thought I knew the provenance, from "Stranded In the Jungle" by the Cadets, 1956. But it turns out that the phrase used in that great work was "great googah-moogah." https://www.youtube.com/watch?v=4h9PbMucPXU at 1:29. Similar, but not usable for authentication.
But this exact vocalization was, so far as I could tell, performed first by Howlin' Wolf in "Goin' Down Slow" in 1961.https://www.youtube.com/watch?v=s865qLWy8-g at 2:41.
Since the Cadets' rendition of this venerable exclamation predates Wolf's by five full years, it may well be argued that we should give credit to them anyway, and consider his later rendition a mispronunciation of the original.