Where does “Norddeutsche” come from?

Norddeutsche (German) comes from German Deutsche, from German Deutscher, from German deutsch, from Old High German tiusch, from Old High German diutisc, from Proto-West Germanic þiudisk, from Proto-Germanic þiudiskaz, from Proto-Germanic þeudō — to swell; to crowd; to be strong.

Ancestry of “Norddeutsche”, step by step

Norddeutsche traces back through two separate lines of ancestry.

via German Deutsche

StepLanguageWordMeaning
1GermanDeutscheGerman; inflection of Deutscher: ## strong...
2GermanDeutscherGerman; inflection of Deutsche: ## strong...
3GermandeutschGerman
4Old High Germantiusch
5Old High GermandiutiscAlternative form of diutisk; popular, vernacular;...
6Proto-West Germanicþiudiskof the people, popular, vernacular
7Proto-Germanicþiudiskazof the people, popular; of the tribe
8Proto-Germanicþeudōpeople, tribe
9Proto-Indo-Europeantewtéh₂people, tribe
10Proto-Indo-Europeantewh₂-to swell; to crowd; to be strong

via German nord

StepLanguageWordMeaning
1Germannordthe north (used without article; a short form of Norden)
2Middle High Germannort
3Old High Germannordnorth
4Proto-West Germanic*norþrnorthern, northernly
5Proto-Germanicnurþraznorth, northern
6Proto-Indo-European*nérbelow the surface, below
Every word from Proto-Indo-European tewh₂-Every word from Proto-Indo-European tewtéh₂Every word from Proto-Germanic þeudō