نحن (Nahnu) usage in the Ancient Near-East

In my college classes, I am studying the Quran and I've noticed that the "We" pronoun used by Allah is typically seen as the "Royal We," but I cannot seem to find that sense of the word prior to the 11th century and further, I cannot find نحن (nahnu) to ever be used in the singular sense by contemporaries of Muhammed; especially in his cultural context. Even the Semitic relative Hebrew term נַחְנוּ (also pronounced nahnu), is always utilized in the plural. I was just hoping someone could help provide me with insight and resources in studying this (preferably works of antiquity written within a century of Muhammed.) With my utmost respect, I thank you all for your time.