You are right there, I think I may have incorrectly copied text from another hint in the quiz. Changed it to Frankish as per Wikipedia attributing the name potentially to its location in the Frankish empire. Thanks for the feedback!
To your point, I did use Wikipedia as my first source for many of these, although I admit I may have incorrectly copied that hint from another in the quiz. With that being said, the article says that "The Old High German word for fireplace, Esse, is also commonly mentioned due to the industrial history of the city, but is highly unlikely since the old forms of the city name originate from times before industrialization." As such, because of the article's noting of Essen in the Frankish Empire, I have changed the hint to Frankish. Thanks for the feedback.