Smells a bit Scandinavian to me. In Norwegian we also use "ur" that way, including "urspråk" (Ursprache, ur-language). We have a different word for origin (opphav), so ur remains a prefix that's difficult for us to translate.
Going by Wikipedia however, the English translation for Norwegian urspråk and German Ursprache is proto-language.
Where's the Orphan Crushing Machine community here anyway