Yes, these are German words. Much of the early topological field literature was by German linguists, so it's common to use the German words.

Also see eigenvector etc.

What realm of science are we? Linguistic or math?

Point stands though. Voorveld, middenveld, achterveld works in Dutch. Don't know what these German words technically mean and so they might have a different translation, but you can / it is common to make this type of compound.

Achterveld works in some German dialects !

According to <https://www.dict.cc/?s=achter>, not only is it northern german, but also "sailor language"! :D English is similar, having "aft" for sailors to say "rear". I know boat people have specialized terms but never thought of it as sailor speak but rather like any other jargon. For some odd reason, the dictcc page also mentions the random fun fact that "achter" is Afrikaans, ignoring where Afrikaans got it from (or rather, who forced it upon them)