Today in Germany the word "Russian-German" is the colloquial name for those Germans who immigrated to Russia and returned to Germany generations later.
The origin of the "Russian-German" is unknown. In history Russian-Germans had several different names: in the 15th century the urban Germans in the Moscow Rus were called "Foreigners" (russ. - "inozemcy") - as well as the Italians or French. During the Russian empire, they were called "nemcy" which today is usually translated as "German-Russians".
The rural German population was invited to settle in the Russian Empire by Katharina II. They followed her invitation and came to Russia between 1763 and the middle of the 19th century. They were lawfully called "Colonists". Due to the decree of June 4th, 1871 the Germans lost their colonial status. They became "settler-owners". In the literature before 1914 the expressions "colonist" and "nemec" appear often.
After the foundation of the USSR (12.30.1922 - 12.21.1911) and the Weimar Republic in Germany (11.09.1918 - 01.30.1933) new expressions for Germans in Russia were used. Statistics from 1926 refer to them as "Germans" (census from 1926 in the USSR look here).
During the conference of German authors in the Soviet Union the newspaper "Literaturnaja gazeta" reports on "Soviet-Germans". (”Literaturnaja Gazeta”. 24, 26,28 März, 1934) Already in 1930 the German department of the ”Allukrainischen Verbandes der proletarischen Bauern- (Kollektivisten-) Schriftsteller“ (All-Ukrainian association of proletarian farmers - (collectivistic) authors) in Charkow, publishes the "Sammlung sowjetdeutscher Dichtung" (Collection of Soviet-German Poetry) in 1931.
In public, Germans in the Soviet Union usually called themselves "Soviet-Germans" until the late Soviet times. Among themselves they are "Deutsche" (russ - "nemec", eng - "Germans") and that is also what it says in their passport.
In Germany we find that Pastor Johannes Schleuning used the name "Russlanddeutschtum" ( eng, "Russiangermanness"). He returned to Germany in 1918 and was committed to supporting the Germans from Russia (Johannes Schleuning, Die Deutschen in Sowjetrussland - Grenz- und Auslanddeutschtum, Heft 24, , S. 7, 10, 11.).
In 1930 the newspaper "Der Russlanddeutsche" (the Russian-German) was published in South America. The expression "Russian-German" was then adapted in a publication ("Volk auf dem Weg", Heimatbücher) by the Landsmannschaft der Deutschen aus Russland e. V. (association of compatriots of Germans from Russia) (founded in 1950).
A critical scientific discussion about a proper term for the Germans in and from Russia started in the Federal Republic of Germany in the second half of the 1980s (Andreas Kappeler, Boris Meissner, Gerhard Simon (Pbls.), Die Deutschen im Russischen Reich und im Sowjetstaat - Köln: Markus 1987.S. 7, 46, 93, 115-118).
After the end of the Soviet Union the Germans in the different countries of the former Soviet Union used the expression "Russian-Germans" most often to define their identity. Therefore, it was obvious that the easiest expression from everyday language and science was the best.