This paper presents a Cognitive-Linguistic and constructionist account of the diachronic development of two highly productive German word-formation patterns, namely ung-nominalization and Infinitival Nominalization. While ung-nominalization suffers a significant decrease in potential productivity and is subject to a growing set of constraints, no such restrictions seem to apply for Infinitival Nominalization. Thus, Infinitival Nominalization might supersede ung-nominalization as the default word-formation pattern for deriving nouns from verbs. It is argued that the diachronic developments are neatly accounted for in a usage-based theory of word-formation change. This account treats diachronic changes affecting word-formation patterns as constructional change, which is in turn conditioned by changes in the availability and prototypicality of construal options evoked by the respective constructions. This view is supported by an extensive empirical study based on corpus data from the 16th to the 19th centuries and by case studies of further developments throughout the 20th century.