From a peer, not from me personally:

The relationship began in the 19th century, in the German-speaking states before unification. German nationalists lacked a unified cultural center, and in order to unify politically, they searched for a cultural unifier beyond German-speaking regions, into other germanic countries. This led to the use of an adaptation of Icelandic mythologies in German literature, such as in Wagner's "Ring" opera cycle and Fouque's "Der Held des Nordens" trilogy. This trend of utilizing Icelandic myths for German cultural unification then re-emerged in Germany under national socialism. This can be seen in Nazi propaganda and in the selective publication and interpretation of Icelandic myths during this time period.

Citation: "The Search for and Construction of a German Identity and Nation in the Nineteenth Century and under National Socialism." Cornell University Press, May 2014. See also: Arni Bjornsson's Wagner and the Volsungs, Ulrike Hafner's Norden und Nation um 1800, Christa Kamenetsky's The Brothers Grimm and their Critics and Children's Literature in Hilter's Germany