Friedrich de la Motte Fouque 
Undine 

According to Wikipedia: ‘Undines or ondines are a category of elemental beings associated with water, first named in the alchemical writings of Paracelsus. Similar creatures are found in classical literature, particularly Ovid’s Metamorphoses. Later writers developed the undine into a water nymph in its own right, and it continues to live in modern literature and art through such adaptations as Hans Christian Andersen’s ‘The Little Mermaid’… Friedrich Heinrich Karl de la Motte, Baron Fouqué (12 February 1777 – 23 January 1843) was a German writer of the romantic style.’