Identical constituent compounds (ICCs) are a prototypical example of extravagant morphology. They violate several constraints and rules of German word formation. Speakers use these violations systematically to highlight specific semantic characteristics of the base noun. Mädchenmädchen ‘girl girl’, for instance, refers to a stereotypical girl. So far, the formal features and the usage of these formations have not been described empirically. This study is based on large corpus data to make reliable predictions about features like linking elements, inflectional behaviour, and the spelling of German ICCs. Furthermore, it investigates which strategies speakers use to make sure that the hearer understands what (in most cases) constitutes a newly formed word.