People cannot help but ask Jupiter Jones what the three question marks stand for, even when they've got a lot of important stuff to be doing today.
“It's a very impressive card, young man. But may I ask what the question marks stand for?”
The three had been waiting for that question. Hardly anyone failed to ask it when they saw the card.
“The question mark, otherwise known as the interrogation mark,” Jupiter said, “stands for things unknown, questions unanswered, mysteries unsolved, riddles of any sort.”
(The Mystery of the Fiery Eye)Earlier:
On Terry Pratchett