catsidhe: [kɑ:t,ʃi:] or "caught-she". gen & pl caitsidhe, n. Irish Gaelic cat = "cat", + sidhe = "otherworldly, magical, fae". Thus, = 'Fairy Cat' or 'Magical Cat'.
In Irish mythology and folklore, a cat which comes from or is associated with the Sidhe, or Fairy realms. Canonically depicted as being larger and more aggressive than normal housecats, and black with a white mark on the chest. It is theorised that they are a mythologising of Kellas cats, which are a crossbreed between domestic cats and European Wildcats.
In this wiki, Catsidhe is a pedant with an unhealthy knowledge of ancient languages.