@Moon

The french anthropologists created a whole mythology loosely based on the octodad of Egypt. It was inspired partially by the short story about the underground race of the Vrill, considered by some to be the first ever scifi story.

It also borrowed from masonic lore, one example being a liberalization of the story of "wisdom bringers" coming from the sea as "fish". Manly P Hall mentions it in one of his lectures.

Those are the main sources, but it's a mish mash.