When I was a junior in high school (10th grade), I turned in an essay in AP US History on one of the Leatherstocking books - probably Last of the Mohicans. In it, I described Cora Munro (again, I'm not sure if this is the right book, but if it was, it was her) as a femme fatale. The teacher of the class was relatively young (and not the teacher we had expected when we signed up for the class - a long story), and she circled the term in my essay.
My response at the time was, "I can't believe she doesn't know what a femme fatale is! How does someone graduate from college, much less get a teaching position, without knowing what a femme fetale is?" I was a very smart 17 year old, and (although I didn't know it at the time) headed for Duke!
Years later - and I'm not sure how long, because this isn't a story I thought of often - it dawned on me that she circled it because I didn't know what the term meant.
I was thinking of this recently because I was rereading a book by Anthony Appiah, and was reminded of an encounter several years ago when I was still teaching. I was vetting essay topics, and a student told me he wanted to write on Appiah as an African philosopher. I responded, "He was born in London, educated in English boarding schools and Cambridge, and has taught in the US for most of his career. Why does he qualify as an African philosopher?"
The student dropped the class, so I never got to have the conversation I wanted to have with him: I was actually reading a lot about African philosophy (and essays about what qualified as African philosopher, by various people including Kwame Anthony Appiah) shortly before this student posed the question; and Appiah had been one of my professors at Duke. I probably spent more time in Appiah's office, talking philosophy, than any other professor I had as an undergraduate. But with regard to my student, I worry that he had the same reaction I had as a high school student: how does this guy not know that Appiah is an African philosopher?
Well, it's not necessarily that he's not, but Appiah himself has problematized the issue. You have to demonstrate that you understand the term.
(Note on the cartoons: the top one is from several years ago, originating in a discussion of Motivational Interviewing - and I ought to write more about that at some point. The second is much older, but I don't think I've posted it before, although I haven't gone back and checked.)