What is "undina"

Undina (sometimes Undine or Ondine) is an opera in 3 acts by Pyotr Ilyich Tchaikovsky. The work was composed in 1869. The libretto was written by Vladimir Sollogub, and is based on Vasily Zhukovsky's translation of Friedrich de la Motte Fouqué's Ondine.

Undina is a genus of prehistoric coelacanth, lobe-finned fish, an intermediary form between sea and land animals which lived during the Late Jurassic period.