General Education Development (GED) tests offer an opportunity for a student to achieve a Certificate of High School Equivalency. The comedian Chris Rock wrote in his book Rock This! (1997):
 
“I dropped out of school. Sorry. I guess I’m not the best role model. Later, I got a G.E.D. You know what G.E.D. stands for? Good-Enough Diploma. A G.E.D. is bullshit.”
 
“Good Enough Diploma” is a backronym (back acronym) of “GED” that has been cited in print since at least 1996. “Good Enough Degree” is another backronymic nickname that has been cited in print since at least 1998.
 
 
Wikipedia: General Education Development
General Educational Development (GED) tests are a group of five subject tests which, when passed, certify that the taker has American or Canadian high school-level academic skills. The “GED” acronym is frequently misused to mean “general education degree” or “general education diploma,” when in fact the GED® brand was developed as a trademark to identify the “tests of general educational development,” a term coined by the American Council on Education, the owner of the GED trademark, in the 1940’s to identify a battery of tests that measure proficiency in science, mathematics, social studies, reading and writing. Passing the GED test gives those who did not complete high school the opportunity to earn their high school equivalency credential, but no state awards a GED per se. http://www.gedtestingservice.com/educators/history
 
The GED Testing Service, a joint venture of the American Council on Education and Pearson, is the sole developer for the GED® test. The test can be taken by paper or on computer, but tests must be taken in person. Jurisdictions award a Certificate of High School Equivalency or similarly titled credential to persons who meet the passing score requirements. Passing the GED® test therefore gives those who did not complete high school the opportunity to earn their high school equivalency credential.
 
Google Books
8 July 1996, Jet magazine, pg. 61, col. 2:
During his break from the “jungle” of the business world, Campbell took the time to attend high school.
 
“I didn’t want a ‘good-enough’ diploma or GED,” explains the star, who has been singing since he was 4 years old.
 
Google Books
Rock This!
By Chris Rock
New York, NY: Hyperion
1997
Pg. 26:
I dropped out of school. Sorry. I guess I’m not the best role model. Later, I got a G.E.D. You know what G.E.D. stands for? Good-Enough Diploma. A G.E.D. is bullshit.
   
Google Groups: alt.fan.scream
Vidpshycho2
8/23/98
(...)
I was just thinking of a joke that GED stood for Good Enough Degree.
 
14 July 1999, Philadelphia (PA) Daily News, “Cassie Hooley, leader in the community,” pg. 28:
Holley was born in Arlington, Va., but was educated in Philadelphia. She got a GED, which comedian Chris Rock jokingly refers to as a “Good Enough Degree.”
   
Urban Dictionary
good enough diploma
GED or General Equivalency Diploma
Having a good enough diploma is better than being a high school dropout.
by Mr. Terrence L. Trezvant Jun 20, 2005
 
Google Books
The Lovesick Cure
By Pamela Morsi
Don Mills, Ontario: Harlequin
2012
Pg. 123:
“Around here we call a GED the Good Enough Diploma.”