Before Frozen 2, what was your headcannon or theory as to why Elsa was born with powers?

While I was satisfied with the explanation we were given, one of the most interesting aspects about Frozen for me was the secret behind Elsa's magic. I had a fun time coming up with explanations of m own, and reading up on what others had come up with.

If I remember correctly, Jennifer Lee herself said that the reason was because Elsa was born on the Winter Solstice, during a planetary alignment. Then again, this was years ago, so I could be wrong.

Here are some of the possible explanations I came up with. Perhaps Elsa was the reincarnation of the actual Snow Queen, who perished years prior to Elsa's birth. Another possibility could be that Idunna was cursed when she was pregnant, by someone who was hellbent on destroying Arendelle, and wanted to do it by its rightful heir. Or maybe the Norse pantheon of Gods had something to do with it, as the franchise does takes place in Norway.