I didn’t know where the strange name “Wizengamot” in the Harry Potter books came from (the Supreme Court of the Wizarding world). Now I found out about the Witenagemot: It was a ring of advisors to the Anglo-Saxon kings of the 7th – 11th century.
Interestingly, J.R.R. Tolkien’s term Entmood is also related to the terminology. Thing is another, earlier type of such political institutions and meetings.