where did the term come from

[bigstuff]

Dear John

[Quizmonster]

The earliest reference to 'Dear John' letters appeared in an American publication in 1945. Here's the exact quote:
"'Dear John,' the letter began, 'I have found someone else whom I think the world of. I think the only way out is for us to get a divorce,' it said. They usually began like that, those letters that told of infidelity on the part of the wives of servicemen. The men called them 'Dear Johns'"
Before this bombshell-letter, presumably poor old �John' or whoever was getting letters which opened: "My Darling John". The �Dear' was the clue as to what was to follow.  �John' was chosen simply because it is an extremely common name and so could mean �Everyman'.