[Skybird]

You may want to discriminate between the ethnic, language-based and juristic forms to define the nationality of a people. The juristic form to do so only is a bureaucratic profanity, and it can but must no correspond to the feeling of identity a given subject may have. Many Turks in modern Germany have formally a German nationality (passport, ID card, citizenship), but do not see themselves as Germans, and some of these may not even want to be seen as that. - This only to illustrate the need to differ between cultural identity and juristic-bureaucratic formality when thinking of "nationality".

The "Germans" get referred to under that name since around the 10th century already. They get mentioned as that in some clerical decrees and written documents related to the Vatican, I think. Since then, the usage of this term spread rapidly in other languages as well.

The birth hours of a German spirit of national identity also is seen in this era, after the battle on the Lechfeld near Augsburg in 955, when Otto I. defeated the Hungarians that until then had time and again raided territories that later would count as "Germany" and for the first time ever saw a strong alliance of feudal leaders and local "chieftains" that before spend more time with fighting against each others instead of the shared bandit-enemy from the Eastern outside. Already before, in the middle of the 9th century, the Franconian empire had been divided into three realms, of which one part, covered the area between Rhein and Elbe. The first king of this kingdom was Ludwig, called Ludwig der Deutsche (the German). The oldest document in German language also is from that time the so-called Strassbourger Eide. Roughly one hundred years later already, the new empire had established itself under Otto the Great, it became later known as the Holy Roman Empire of German Nation.