A boy of about 10 comes to the desk with That Book of Perfectly Useless Information, holds it up to me, and says,
Do you have any other books of useless trivia, because I really like useless trivia and want to learn more useless trivia.
So naturally, knowing we have lots of books like this, I spin my computer monitor towards him and type in a keyword search, limited to our library, for "useless trivia." I click the search button, and am instantly embarrassed by the result.
Oops. But his response was classic - absolutely dead-pan, he just says "no, I'm not interested in that."
Trying quickly to recover, I searched for the book he has in hand, explaining that each book is assigned subjects, which will link to more books on that same subject. It does, and a bunch come up - all at the same call number of course, so I walk him over to that shelf and help him find a few good ones. He is pleased and goes off to the Circulation Desk to check them out.
Now, I go back to the catalog record for the book he had, because something caught my eye. The subject heading for that book was "Handbooks, vade-mecums, etc."
I don't think I've ever seen this particular subject heading before, and I didn't know what "vade-mecums" meant. I was half expecting it to be Latin for "useless trivia," but according to Merriam-Webster, it means "a book for ready reference." Amazing that in all my time as library student and reference librarian, I hadn't come across that term before. I guess you really do learn something new every day.
(Incidentally, the Latin for "useless trivia" is frustra turpis, according to Google Translator.)