This article investigates the diachrony of the adnominal genitive in written German by analysing its usage in a diachronic corpus of sermons from the Upper German dialect area spanning the time from the 9th to the 19th century. The wide temporal scope allows for a better assessment of the events relating to the genitive’s disappearance from spoken German in Early New High German and its successive rise in written German. While sermons make it possible to cover such a long time frame on a consistent basis in terms of genre and region, they are themselves subject to stylistic trends as a genre that combines characteristics of both spoken and written language, which is valuable for gaining insights in the divergent development of genitive use between these poles. In order to characterise this divergence better, I use the concept of polarisation, which describes the differentiation of linguistic usage between disparate contexts such as speech and writing. It becomes clear that the changes in genitive use found in the corpus cannot be viewed independently of sociopragmatic factors and their impact on the stylistic shape of the texts.