I'm about halfway through this book and have yet to find more than a handful of stories that I would call "fairy tales" rather than legends, or parallels to familiar fairy tales. There was one story that started like Rumpelstiltskin, with a lazy daughter who didn't want to spin, but instead of being told to spin gold and helped by a funny looking little man, she was cursed to go spin in the Moon.
But I'm always fascinated by mermaid tales. And if there's anything we know about mermaid folklore, it's that these mermaids are entirely different than Hans Christian Andersen's suffering, lovesick young girl. Mermaids are dangerous and creepy, known to entice men to their lair below the surface, where the men often forget their families for a time. If they do return to land, they are often cursed, as are the offspring of men and mermaids.
As far as origins, according to the beliefs of the people of Germany's Upper Palatinate, "The Mermaid was once a fair and beautiful princess, but also very cross and fitful, whereupon her own father cursed her and banished her to the sea where she would be able to do whatever she wanted. Thus she became half woman and half fish, living in the sea, where she announces through a very distinct song that a storm will occur in 24 hours."
Here's a shorter mermaid tale from the collection that gives you a good idea of what they are like. Apparently, the Mermaid in this tale demanded some sort of regular human sacrifice from sailors. Although this Mermaid shows mercy there is still a very dark side to interacting with sea maids:
"A ship on the ocean had run out of corpses for the Mermaid, and it had to be decided by lot who among the crew should be sunk into the waters. A handsome young man drew the lot. But the Mermaid had mercy on him because his bride was already waiting for him with longing on the shore of the country nearby, and she carried him to the shore, and gave him as a present three little bags full of gold, silver, and pearls. In return, the bridal couple had to promise her the seventh child born to them.
When that child came into the world, the Mermaid appeared and took delivery of it; for she is allowed to assumed human form on every seventh day of the week; she comforted the grieving parents by assuring them that the little one would be treated well.
A long time had passed, when the oldest son, against his parents' will, chose a poor girl for his wife, and they cast him out. Thereupon the Mermaid reappeared, brought back the seventh child, who had grown up to become a handsome young man, and brought rich presents for the unhappy bridal couple, but once again, in return for their promise that the seventh child of the marriage would belong to her.
To this day, the Mermaid is the kind and protective spirit for this family; when misfortune strikes, she comes to help; but always she has a child from the family circle with her in her palace of glass under the sea, and once this child has grown into a young man, she puts him back and takes another."