"Duc de Sully" is a proper noun and a specific title or name. It is not a general word nor a term that has synonyms. However, the "Duc de Sully" was a French statesman and military leader during the reigns of King Henry IV and Louis XIII. Therefore, some related terms or words that could be associated with "Duc de Sully" are French monarchs, government officials, diplomats, military commanders, statesmen, policymakers, and historians. Additionally, the "Duc de Sully" is known for his memoirs called "Memoires de Sully," which chronicled his life and experience, hence the word autobiography could be related to his name.