Dear John letters

Dear John letters are breakup letters, specifically ones sent to end a romantic relationship from a distance.

The term originated with letters from wives or girlfriends to soldiers serving overseas, delivering news that the relationship was over.

The generic "John" emphasizes the cold impersonality—the recipient is just another man being dumped by mail.

Now used for any written rejection of a partner: She got a Dear John letter while he was on his business trip.