The two language variants of Norwegian (Bokmål and Nynorsk) have translated their language variants inconsistently:
Currently in CLDR:
So the Nynorsk translation omits "norsk" ("Norwegian") from the translation, while Bokmål includes it. It is context dependent on whether it's needed or not, but the safer bet would be to include it. Either way, the two variants should like take the same approach here.