Ludwig Rellstab

Heinrich Friedrich Ludwig Rellstab (13 April 1799 – 27 November 1860) was a German poet and music critic. He was born and died in Berlin. 
The first seven songs of Franz Schubert's "Schwanengesang" have words by Rellstab, who had left them in 1825 with Beethoven, whose assistant Anton Schindler passed them on to Schubert. His work was also set to music by Franz Liszt. 
He is also known to have given Beethoven's Piano Sonata No. 14 in C-sharp minor, Op. 27/2 its famous nickname "Moonlight Sonata".