Green’s Dictionary of Slang

1. a letter concluding a relationship, usu. sent by the woman and received by the man, often in prison or serving in the forces.

a.1945		in Campbell & Campbell War Paint 120: [aircraft nose art] Dear John.
1951		R. Leveridge Walk on the Water 264: Dubois had received a ‘Dear John’ from his wife.
1958		C. Lee diary 2 May in Eight Bells & Top Masts (2001) 107: Ainslie had a Dear John today. His girlfriend’s chucked him.
1961		Mad mag. Dec. 27: I just got a ‘Dear John’ letter from my wife.
1963		N. Dunn Up the Junction 105: He got a Dear John – a letter from his bird saying she didn’t want to know no more.
1973		in C. Browne Body Shop 35: Three months after I was in Nam I got a Dear John from my girl.
1988		J. Healy Grass Arena (1990) 166: Another morning, a guy got a ‘Dear John.’ Fired himself off the fives, landed in the safety net.
1995		J. Cameron Vinnie Got Blown Away 88: Soon after sentence I got a Dear John off that Kelly.
1999		T. Fontana and B. Winters ‘U.S. Male’ Oz ser. 3 ep. 5 [TV script] Then of course there’s the Dear John letter, or Dear Jane, as the case may be. When your loved one tells you how much you fucked up her life.
2000		Indep. Rev. 21 Feb. 8: I immediately sent Ash a ‘Dear John’ letter.
2006		B. Matthews Intractable [ebook] [He] opened the door to another escape plot when he got a Dear John letter.
2024		J. Meades Empty Wigs (t/s) 634: He tearfully regretted that his ‘best girl’ was no longer his best girl. She had sent him a Dear John.

2. (N.Z. prison) a visit from a female partner that fails to materialise.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 53/2: Dear John n. a situation in which an expected visit from an inmate’s female partner does not eventuate.