Few of the statements penned by philosophers have become as infamous as the "God is Dead!" of Friedrich Nietzsche. This study is not concerned with the reasons why this phrase is so popular. Instead, I would like to delve into the prehistory and partial genesis of the concept, something Nietzsche adopted from a previous tradition. Apart from known examples of theses on the death of God by Hegel, Schelling or Jean Paul, I will shed light on some of the confusion surrounding the phrase deus est mortuus in Mediaeval Christian liturgical literature and mysticism, with roots reaching back to Neoplatonism. The goal of this study is to point out that this phrase about the death of God had no significant constitutive meaning for Nietzsche but was, instead, a relatively common literary and rhetorical topos among other culturally diagnostic expressive elements. Nietzsche used it as an illustrative shortcut when describing the intercultural processes of his time, with no ambition to originality, instead, with the clear intention of shaking up the (non)thought of the comfortable bureaucrats and legalistic petit bourgeois of Germany in the late 19th century.