Well the Nazi party believed that many Germans were of Nordic blood. The SS rules claimed it was strictly for Germanic men of Nordic descent which shows that they believed some Germans shared the same racial characteristics as Norwegians.

Broadly there was a movement during the unification of the German Empire to create a new national folklore and mythology which led to the creation of a wave of new fairytales and in particular a resurgence of the Nordic sagas and mythology, and Icelandic poetry. The decline of organised religion meant that German nationalists tried to push neo-pagan religion based upon Nordic myth as the new religion of the new German state instead of Christianity, and the resurgence of spirituality was seen by German nationalists as an alternative to the British and French enlightenment.

This grew popular amongst Volkish movements which Nazism later pulled from. Joerg Lanz claimed that Hitler bought his magazine Ostara. We only have Lanz's word for this but Ostara did prophesized the return of a race of Nordic god men and push the importance of the purity of Nordic blood and the decline of the Aryan race brought about by Judaism, feminism, socialism and liberalism which seems similar to later Nazi doctrine.

Himmler and the SS' ideas seem to have come from Richard Walther Darre of the Artaman League - a Volkish movement Himmler was also a member of. Darre argued that all empires had been ruled by a Nordic aristocracy but that each aristocracy had allowed itself to dilute its blood or go into decline. He argued that the Germanic spirit had been weakened by the ideas of the enlightenment, collectivism, freemasonry, and Christianity whilst Germans intermingled with Jewish and Slavic blood. In his view Germany needed to create a new aristocracy and this needed to be the Nordic peasantry who remained uncorrupted.

Source: The SS a New History - Adrian Weale

Hitler's Monsters - Eric Kurlander