I'm convinced that the Noah flood was a retelling of the Babylonian myth.
This article gives a good overview:
http://www.geocities.com/paulntobin/floodorigins.html
I was struck by this paragraph in the conclusion:
Was Noah actually a historical person? Again archaeological evidence supplied the answer. In 1933 clay tablets were discovered in Mari, an ancient city in the Mesopotamian plain. In these tablets (there were about 20,000 discovered), the name Noah appeared many times; as the name of a god.[7] In fact Noah’s name is actually a musculanisation of the goddess of rain, Nuah
I read "musculanisation" as a typo for "masculanization".
The tie in with the rainbow sounds like an explanation of why there are rainbows. Maybe someone put the two stories together to expand on that?
lfen