I've spent some time considering the associations of Beethoven's D minor Piano Sonata Op. 31 No. 2 with "Der Sturm" - as referenced by the not-too-reliable Anton Schindler. In his book on the composer, whose amanuensis he briefly was, Schindler recalled asking Beethoven for the "key" to this enigmatic work and being told "Read Shakespeare's 'The Tempest'" (German: 'Der Sturm').
One has doubts, of course. Nothing with a nickname can ever be totally trusted, unfortunately, and when it's Schindler providing the basis, even less so. I was considering an alternative theory: that in fact Beethoven - assuming he said anything of this kind at all to Schindler, perhaps inaccurately remembered by the latter - had been referring to the poet Christian Christoph Sturm, whose writings he held in high regard and who often considers the wonders of nature, the place of humanity within it and the relation of both to God and the divine order, all of which seem more than pertinent to the atmosphere of this piece.
However, try reading 'Full Fathom Five' from The Tempest and remember it is sung by Ariel, the spirit of the air, and then listen to the slow movement of the D minor sonata. The beginning seems almost to serve as the introduction to a song; then the theme arrives, deep set, full fathom five down, with a high, seagull-like figure decorating the upper register and casting perspective. The harmonies become richer and stranger; and a figure appears in the bass (sometimes, also, the treble) that flickers like a drum roll, or a distant tolling bell.
Both theories actually work. Neither is strictly necessary. But they are wonderful to ponder. Enjoy.