Lily is chatting with her classmate Becky in the common room of their dorm.

    Lily: Hi, Becky. Can I ask you a question?

    Becky: Sure!

    Lily: What's an eponym?

    Becky: Ooo, tricky. Because it means two things, opposite but related.

    Lily: Okay.

    Becky: You know the book, "The Odyssey?"

    Lily: Yes...

    Becky: It's about the travels of Odysseus, right?

    Lily: Right.

    Becky: So we can say, "Odysseus is an eponym of 'The Odyssey.'"

    Lily: Uh-huh.

    Becky: But we can also say, "'The Odyssey' is an eponym of Odysseus."

    Lily: Oh, it's kind of like "namesake."

    Becky: A little bit, yeah. But for example, a lot of city names are eponymous.

    Lily: "Eponymous"--the adjective form?

    Becky: That's right.

    Lily: So, for example, Saint Francis was the eponym of San Francisco.

    Becky: Yes, and Constantine of Constantinople. Other ones can be kind of surprising.

    Lily: Like what?

    Becky: Well, have you ever heard the word "algorithm?"

    Lily: Sure! That's a procedure for solving a problem with numbers.

    Becky: That's it! In fact, the word comes from the name of a Persian mathematician of the Middle ages, al-Khwarizmi.

    Lily: Fascinating!

    Becky: I thought so. By the way, it was from his work that we get the word "algebra," and the use of so-called "Arabic numbers."

    Lily: That means our regular number characters--1, 2, 3, and so on, right?

    Becky: Yes, that's right.

    Lily: Cool. Can you tell me some more eponyms?

    Becky: Well, any time a band names an album after itself, that's eponymy.

    Lily: Or when a book is named after one of its characters, like "Harry Potter" and so on?

    Becky: Yup. Lots of diseases are named after doctors who discovered or first described them.

    Lily: Like "Parkinson's Disease" or "Asperger syndrome."

    Becky: Uh-huh. The Caesar salad was named after Caesar Cardini, a restaurant owner.

    Lily: Not the Roman leader?

    Becky: No, silly! And there are lots of company names, like "Hewlett-Packard"--

    Lily: HP!

    Becky: And "Wal-Mart" and "Sam's Club" are both named after Sam Walton.

    Lily: Got it. There are cars named for Henry Ford, aspirin named for Friedrich Bayer, and catsup named for Henry Heinz. What about common items?

    Becky: Let's see... The sandwich is named after the Earl of Sandwich. And the saxophone after its inventor, Adolphe Sax.

    Lily: It seems like we're surrounded by people from the past!

    Becky: Of course! And we haven't even talked about hospitals, schools, government buildings, parks, monuments, and all the other things named after famous people.

    Lily: Well, I think I understand now, Becky. Thanks a lot!

    Becky: My pleasure.