oh dear sweet heavens! this is so sultry and beautiful
from another yt video of this etude (musicology and history story/remarks remains to be confirmed)
A little background on this etude:
Bortkiewicz's lifelong friend, Hugo van Dalen, the Dutch pianist and composer (1888-1967) told him that it was through his playing of the Etude Op. 15, No. 8 that he had met his wife. She liked the piece so much that she came up to van Dalen to ask the composer's name. This acquaintance led to their marriage, as a result of which Bortkiewicz unofficially named this etude the Verlobungsetude or Betrothal etude.