Board Thread:Theories and Speculation/@comment-3568954-20150630211538/@comment-28861328-20150701231408

It makes more sense that, if he was inspired, it came from rabbits. Kaguya, the first known user, was called the "Rabbit Goddess" and has a strong rabbit theme due to her affiliation with the folk-character of the same name.

EDIT: Furthermore, just because Kishimoto didn't plan the end of the series from the get-go, doesn't mean Kaguya (or some similar concept) wasn't in some of the notes he had for the lore of his story. It is very rare that an author, of anything, actually plans their story from start to finish, with all the details in between. Secondly, like I said, Kaguya or a similar concept very likely existed somewhere in Kishimoto's notes as a backstory character to explain the Byakugan and/or chakra, and Kishimoto later decided to use her as the final villain.