Here's why it's called the "circular file":
* The "circular file" is a slang term for a wastebasket or trash can.
* The term suggests a circular motion, as if you are tossing something into a bin and it's gone forever.
So, when you say "put this one in the circular file," you're essentially saying you're done with it and have no intention of dealing with it further.
Example:
* "I told my boss about my new ideas, but he just said, 'Put this one in the circular file.'"
This means the boss dismissed the ideas entirely and wasn't interested in hearing more.