一、
To Whom It May Confound::
Dear Word Detective: I recently received an e-mail from my brother in which he told me he wouldn't be coming to visit me this weekend because he had received a "Dear John" letter from his girlfriend. I gather that she dumped him, but why "Dear John"? His name is Craig. -- Frank Golding, Brooklyn, NY.
Well, you could suggest to your brother that his girlfriend actually meant to dump one of her other boyfriends, but he's probably not in a mood for humor.
There are worse things out there in the postal system than junk mail, and one of them has been a fixture of life since the Second World War -- the "Dear John letter." A "Dear John letter" is a missive penned by one's paramour in which she (or he) abruptly announces an end to the relationship. "Dear John letter" entered the public vocabulary via the military during WWII, a conflict which sent millions of husbands and boyfriends overseas, many of whom discovered that absence, especially prolonged for years, often does not make the heart grow fonder. As a Rochester, NY newspaper explained in 1947:
"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."
The pain of receiving such a letter in the midst of a war in a far-away land must have been made all the worse by the stilted salutation apparently common in such messages -- "Dear John," rather than the expected "Dear Johnny," "My Dearest John" or simply "Darling" -- and probably explains how "Dear John letter" came to stand for the entire phenomenon of long-distance postal dumping.
"Dear John letter" may also be the key to another popular phrase, "That's all she wrote," meaning "That's all there is" or "That's the end of it." According to some authorities, a joke current among servicemen during WWII had a soldier opening a letter and reading it aloud to his comrades. "Dear John," he reads, and then abruptly stops. His mates urge him to go on reading. "That's all she wrote," he says, holding up a letter blank except for the deadly salutation.
資料來源：
The Word Detective, Issue of September 6, 2002
http://www.word-detective.com/090602.html#dearjohn
二、
DEAR JOHN LETTER
[Q] From Pien Metz: “As a non-native speaker of the English language, I still wonder where the phrase Dear John letter comes from. I have always taken it to be a letter in which the recipient is told a love affair is over, but I might be amiss.”
[A] No, you have it right. It’s conventionally a letter from a woman to a boyfriend or husband saying that all is over between them, usually because the woman has found somebody else. A much more recent phrase that reflects today’s sexual equality is Dear Jane letter.
The expression seems from the evidence to have been invented by Americans during the Second World War. At this time, thousands of US servicemen were stationed overseas for long periods; many of them found that absence didn’t make the heart grow fonder. The unhappy news was necessarily communicated in a letter. A writer in the Democrat and Chronicle of Rochester, NY, summed it up in August 1945:
“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”.
Why Dear John? That isn’t entirely clear but a couple of pointers give a plausible basis for it. John was a common generic name for a man at this period (think also of terms like John Doe for an unknown party to a legal action). Such letters were necessarily written in a formal way, since any note of affection would obviously have been out of place. So a serviceman getting a letter from his wife or girlfriend that started so stiffly knew at once that a certain kind of bad news had arrived.
Several subscribers have mentioned a song on the theme of receiving a “Dear John” letter, suggesting it was the origin of the phrase. However, online sources say it appeared only in 1953, several years after the phrase had become established. A more plausible source was suggested by Dick Kovar—in a pre-World War Two radio programme called Dear John, starring Irene Rich, which was presented as a letter by a gossipy female character to her never-identified romantic interest and which opened with these words. Proving a link is likely to be impossible, but it’s conceivable this played a part in the genesis of the term.
資料來源：
World Wide Words
http://www.worldwidewords.org/qa/qa-dea5.htm