There is an image of this cultivar on the Hosta Library. From the photo on the HL website, it appears to be a medium size hosta with wavy, lanceolate, yellow leaves and a narrow green marginal variegation. This non-registered cultivar was originated in Japan and introduced by Fritz Köhlein of Germany. 

This German cultivar name could refer to many different things but we suspect that the most likely candidates would be Das Rheingold, the 1869 opera by Richard Wagner or to the European international express train of that name.