There are spoilers, express or implied, in this post, so if you intend to go read The Swan Maiden (http://www.portiris.com/) ... do that before you read this.
The Swan Maiden came about through an intersection of three distinct thought lines:
First, the monthly Fantasy-writers.org challenge, the topic being madness. Now, when the topics are fairly simple (and sometimes when they aren't), I liked to take them and give them another twist. So I decided to construct a storyline where the take on this theme was, "Just because you're right doesn't make you sane." So the story appears to go back and forth on whether or not Alita is crazy, and in what fashion.
Second, Golden Bough's beautiful, haunting, "Song of the Swan Maiden." It leapt immediately to mind as I was considering the topic. The inspiration is more thematic than direct, though there are a few specific elements of the plot that were influenced by this lovely ballad. It's contemporary, not traditional - written by their harper, Margie Butler.
Third, my world files. I went straight for one of my more bizarre scrawls, a fantasy / sci-fi post-apocalypse setting. You see only a very tiny fraction of this setting in The Swan Maiden. Some of the concepts contained within seemed ideal for this story.
Since the lyrics for "Song of the Swan Maiden" don't appear to be out there, I've written them below and hope I don't get into trouble for it. To affirm, these are not mine, and I'll be happy to remove if this is a problem.
The people of the town say she's crazy
The people of the town say she's mad
As she wanders by the shore long hours
Dreaming of the love she once had
Many nights I've seen her weeping
Underneath a darkened sky.
Many days I've heard her singing
The same sad lullaby.
I have wandered by the ocean.
Just to hear her mournful song.
Her heart so filled with longing,
To the night she does belong.
In the cold light of the dawning,
Just as the morning sun did break,
I thought I saw her swimming
With the swans upon the lake.
On that silent day she vanished,
Of her song there was no trace.
I walked the cliffs and meadows,
I searched in every place.
They say some strange enchanted magic
Has taken her away.
Bewitched so by her sorrow
They say she'll always stay.
Some say that she's become a swallow,
And out to sea has flown.
Some say into a willow,
Weeping, she has grown.
Through the seasons I will wander,
Through the heather, through the snow.
I'll sing it to the willow,
Surely, she will know.
I'll sing it to the morning,
The song that she has given me,
Likewise into the evening,
Someday I know she'll see.