Germany:
Named Germania by the Romans. The land east of the Rhine. Late Latin germanus = brother, from ther span. hermano. Might have a special sense, cf. lex Rhodia de iactu, where "germanitas" denotes the sharing of saved goods brotherlike. The German etymology is ger-man = spearman. But God knows best. Deutschlandis a recent name. In medieval times we had a King of the Germans or German King, but he reigned the Holy Roman Empire of the German Nation.
It was followed by the German Federation (of 33 states including four republics). 1870 followed by the German Reich, the name remained until 1945. In 1949 we meet Deutschland for the first time as a name for a political unity in "Bundesrepublik Deutschland" (Federal Republic of Germany). The name was given by the National Assembly to the new state.
The National Anthem of the Reich since 1919 starts with Deutschland, Deutschland über alles, where Deutschland denotes not a state, but the lands where the German language is used. (Since 1949 we only sing the 3rd stanza starting with "unity, justice and liberty"). The song was written shortly before 1848 in Helgoland, then a British island.
Allemagne, Alemania:
Derived from the Allemanni, a German tribe on the upper Rhine, partly in Alsatia, with a special dialect, name given by the French. France: In German Frankreich, Empire of the Franks. The Franks were not a tribe, but a confederation of tribes. The Empire was divided into three parts after the death of Charlemange between his three sons; the eastern king inherited the title of Emperor. The middle part was later on divided between the eastern and western parts. Schweiz, Svizzera, Switzerland: Derived from Schwyz, one of the original cantons. The name is used by the Swiss only for their language Schwyzerdütsch = Swiss German. They call themselves Eidgenossen, Confederates (sworn together), in the Confederatio Helvetica. As noted correctly before the Helvetii were an Alpine tribe; when Switzerland was occupied by the French under Napoleon they formed the Helvetian Republic.
Dutch:
Clearly a name given by people who can't pronounce "Deutsch" correctly. Not only used for Netherlanders, but also for German immigrants in the USA with their hybrid language Pennsylvania Dutch. Note that the Netherlands belonged to the Roman Empire of the German Nation in former times like the Helvetian Confederates.

Wilfried