The Duden dictionary defines Herrschaftswissen as knowledge that a person has acquired through their position or official duties and that is not accessible to others. It serves the exercise of power over others. The DWDS dictionary defines it as knowledge gained through individual experience, or kept from the public by restricted access, that someone can use to their own advantage. German Wikipedia adds that in its widest, colloquial sense the word is critical and comes close to cunning. It then means a lead in knowledge that someone uses to secure their position.