While I was looking up “terpsichory”, I came across “Melusine”. I decided to share the Wikipedia explanation. I just liked the idea of such a strange creature, hope you think so too.
For other uses, see Melusine (disambiguation).
Mélusine (French: [melyzin]) or Melusine or Melusina is a figure of European folklore, a female spirit of fresh water in a holy well or river. She is usually depicted as a woman who is a serpent or fish from the waist down (much like a lamia or a mermaid). She is also sometimes illustrated with wings, two tails, or both. Her legends are especially connected with the northern and western areas of France, Luxembourg, and the Low Countries.
Mallaband-Brown 