History of the Wagner Tuba
It was in the mid 19th century that instrument maker Adolphe Sax produced the instrument, demonstrating it to German composer Richard Wagner when they met (circa 1853). Wagner was struck by the horn's rich sound and soon began to incorporate it into his orchestral composition.
At the time he met Sax he had just begun work on "Das Rheingold" and it is in the opening of Scene 2 where we find him using the instrument to announce the Valhalla theme. Indeed, "The Ring" became the first major orchestral work to feature the instrument and Wagner had a set of 4 built specifically, having written for a quartet in 2 pairs: Bb (tenor) and F (bass). Hence why it became known as the Wagner Tuba.