Language fil in Theme folder SimpleMarket

Hello,
I want to change the text in the footer "Go back to top" and copied the "en_en" (Gettext message fil) and the "en_en" MO-fil to new files for Norwegain text, and named the two files "nb_NO", that does not work.
What should the name of these files be for picking up Norwegian text?

Thanks,

Regards,
Ingvar