I had a head of department once whose son was something unmemorable and daughter was
Avalon. That was what they called her - no nn. I've forgotten most of the story, but they were an Irish family originally and the husband chose
Avalon because of something related to music, whether a singer, a group or a song I no longer know.
I dislike geographical names in general, but mythological ones are worse so I'd find both
Avalon and Atlantis unusable in the extreme!