@Kurozumi Wiwi Nami is sweedish. Birka is in sweden.
Birka is also two place in op: (1) a city in the moon; (2) enel's hometown
Gan Fall told about the existence of another and safe entrance to the sky island. He is referring to Elbaf's tree.
The costumes of Birka in real life is Viking's costume. Elbaf's costumes are viking like. Why Enel wanted to become a god, why he removed his wings and why he put drums in his backs?
Because he lived in Birka, above Elbaf and know about the myth of god Nika. Enel removed his wings and put thr drums of liberstion because he wanted to become like Nika.
We don't know where Nami born. She is from which Birka? Moon's Birka or Sky Island Birka?
Nami doesnt have wings, so she is not from sky islands. Enel chose btw all people Nami to go with him to the moon. I believe Nami born in the moon. And I also believe she is the certain "princess of the moon", a song that Hyiori plays along Wano arc. That song is not a Wano song. Oden said he never heard that song before. So who taught Hyori about that song? Toki, of course. Toki is from void century and her surname "Amatsuki" means heaven moon.
I think people from Birka's moon didnt have wings. So Nami could be from there
*Its also important to note that this Birka moon is much older than the sky island
So Elbaf, Birka, Moon, Nami, Enel and Nika are all connected