A probe into the changing perceptions and classifications of Silesian (i.e. the Slavic dialect and the Slavic-Germanic creole of Upper Silesia, or both construed as the ethnolect of the Silesians) during the nineteenth and twentieth centuries, as most saliently influenced by the mutually nullifying competition of German and Polish ethnolinguistic nationalisms. This competition opened the space for the rise of the Silesian national-cum-regional movement, which sometimes undertook the task of codifying a Silesian language. Such codifications were frustrated during the periods of dictatorship and totalitarianism, which lasted in Upper Silesia from 1926/1933 to 1989. Berlin and Warsaw suppressed the possibility of the rise of a Silesian language, perceived as an ideological threat to the ethnolinguistic legitimization of German and Polish national statehood. Today, Warsaw dislikes the recent popular grassroots project to codify Silesian as a language, but, under the democratic conditions enjoyed in postcommunist Poland, the state administration has no legal means to suppress this project. The codification of Silesian gathered pace at the turning of the twenty-first century, due, among other reasons, to the rapid spread of access to the Internet. However, without the state's blessing and support, the outcome of the codification project, remains, at best, uncertain.