Nacht und Nebel
The alliterative hendiadys "Nacht und Nebel" (German for "Night and Fog") is documented in German since the beginning of the 17th century. It was used by Wagner in "Das Rheingold" (1869) and has since been adopted into everyday German (e.g. it appears in Thomas Mann's "Der Zauberberg"). It is not clear whether the term "Nacht-und-Nebel-Erlass" ("Night and Fog directive") had been in wide circulation or used publicly before 1945. The designation "NN" was sometimes used, however, to refer to prisoners and deportees ("NN-Gefangener", "NN-Häftling", "NN-Sache") at the time. The abbreviation "NN" was otherwise well known in German to mean "nullus nomen" ("without name" for security reasons), similar to the English NN for "nomen nescio".