What does the expression I'll put this one in the circular file mean?

The expression "I'll put this one in the circular file" is a euphemism for discarding or ignoring something, often referring to a piece of correspondence or a document. The "circular file" humorously implies a wastebasket or trash can, suggesting that the item is not worth keeping. It conveys a sense of dismissal, typically used in a professional context when something is deemed unimportant or irrelevant.