So, that casual reference to Biollante's name coming from Norse myth has bugged me for a while. After using my Google Fu, that line seems to be almost total BS - but I did find a much likelier source. The closest I could get to a Norse source is , but that's still a long way off from Biollante. But you know what name isn't far off? Iolanthe, who's a character (based on a real person) from . The plot doesn't have much connection to Godzilla or Biollante, but the character does live in a garden. Also, take a look at this poster:
This catches my attention.
EDIT: But wait, there's more! I guess I should have looked at the Gilbert and Sullivan opera while I was at it. It's actually a little more pertinent to Biollante's origin: this work's Iolanthe was exiled from the fairy realm for marrying a human male, and also has a son who's half fairy and half human. It does fit the crossbreeding theme, with Biollante being the combination of Godzilla cells, Erika, and a rose.