Just some more thoughts (I am not a historian, so don't rely on whatever I write) about Germany/Allemagne/Deutschland:

In the area nowadays known as Germany many tribes lived.
Especially in the south/southwest (i.e. near France) a tribe called "Alemannen" - this lead to the French name Alemagne. (not sure about the numbers of "l" right now).

In other areas, a tribe called "Teutonen" lived. Teutonen -> Deutsch

Germanen: afaik is derived from the fact that they used a weapon called "Ger" which is spear in English, so it should translate to spear-men.

In slavic languages, German is "nemes" or "nimis" or "nemec" - don't ask me where that comes from.

MudGuard (not a German, but even better: a Bavarian)