This paper investigates a type of empty morph that attaches to noun forms and that will be called “noun affix” here. Based on six case studies from unrelated African and American genera, I arrive at a diachronic typology of noun affixes that in many ways confirms and in other ways expands on the findings of Joseph Greenberg, whose work on the topic remains the yardstick. One claim is that noun affixes may emerge directly from gender markers and that this is reflected in the paradigm size of noun affixes. Furthermore, there is evidence for the idea that old noun affixes may be repurposed for the creation of phonologically minimal word forms. The main interest of this study is in what the development of noun affixes reveals about processes of grammaticalization. The current literature mostly focuses on the fact that grammaticalization is initiated by semantic changes (mostly semantic reduction) rather than by formal changes. This raises the question of whether semantic reduction is also completed before formal reduction. The noun affixes provide compelling evidence for this idea and thus suggest that empty morphs may arise via grammaticalization. This runs counter to approaches on which form and function erode in parallel.