Gilles Deleuze, Felix Guattari, and Isabelle Stengers fought against a state-controlled form of science and saw “nomadic science/concepts” as a way to escape from it. The transnational history of the term milieu marks a good opportunity to contribute to another theory of nomadic vocabularies. Traveling from France to Germany, the word milieu came to be identified as a French theory. Milieu was seen as an expression of determinism, of the connection between the rise of the natural sciences and the rise of socialism, and it deterred the majority of German academics. Umwelt was thus coined as an “antimilieu” expression. This article defends a “transnational historical semantic” against the Koselleckian history of concepts and its a priori distinctions between words and concepts. Instead of taking its nature for granted, a transnational historical semantic investigation should analyze the terminological and national status given to the objects of investigation by the term's users.