Premise: "Ellens dritter Gesang " ("Ellens Gesang III ", D. 839, Op. 52, No. 6, 1825), in English: "Ellen's Third Song", was composed by Franz Schubert in 1825 as part of his Opus 52, a setting of seven songs from Walter Scott's popular epic poem "The Lady of the Lake", loosely translated into German.
Hypothesis: Franz Schubert's Ellen's Third Song became a very popular song in the 1800s.