Pontiac is an automobile brand that began in 1926 and was discontinued by General Motors in 2010. The name “Pontiac” was associated with a racial slur backronym (back acronym)—“Poor Old Nigger Thinks It’s A Cadillac.” The backronym has been cited in print since at least 1984.
 
Jesse Jackson ran for U.S. president in 1988, and his Secret Service code name was “Pontiac.” American folklorist Alan Dundes pointed out the racial slur that some had made of the name “Pontiac,” and the Secret Service code name made national news. The ‘Pontiac” backronym is still frequently cited, along with other variations such as “Poor Old Nut Think It’s A Cadillac” and “People On Narcotics Think It’s A Chevy.”
 
   
Wikipedia: Pontiac
Pontiac was an automobile brand established in 1926 as a companion make for General Motors’ Oakland. Quickly overtaking its parent in popularity, it supplanted the Oakland brand entirely by 1933 and, for most of its life, became a companion make for Chevrolet. Pontiac was sold in the United States, Canada, and Mexico by General Motors (GM). Pontiac was marketed as the performance division of General Motors for many years, specializing in mainstream performance vehicles. Pontiac was relatively more popular in Canada, where for much of its history it was marketed as a low-priced vehicle.
 
On April 27, 2009, amid ongoing financial problems and restructuring efforts, GM announced it would discontinue the Pontiac brand by the end of 2010 and focus on four core brands in North America: Chevrolet, Buick, Cadillac and GMC. The last Pontiacs were built in late 2009/early 2010, with the final dealer franchises expiring October 31, 2010.
   
Google Books
Maledicta
Volume 7
1984
Pg. 297:
What do the initials in PONTIAC stand for? — Poor Old Nigger Thinks It’s A Cadillac.
 
Google News Archive
25 June 1988, Pittsburgh (PA) Post-Gazette, “Code for Jackson racist?,” pg. 3, cols. 1-2:
WASHINGTON (AP)—Some people are claiming the radio code name, “Pontiac,” that the Secret Service uses for Democrat Jesse Jackson has racial overtones, but a Secret Service spokesman said yesterday that Jackson doesn’t think it’s racist.
(...)
Jackson aides tried to trace why Jackson had been assigned that name after learning that folklore expert Alan Dundes said “Pontiac” is a slur—the punchline to a series of racist jokes collected by his students at the University of California, Berkeley, said Jackson’s national political director, Frank Watkins.
 
Pontiac, usually associated with a car and a city in Michigan, is also an acronym for “Poor old nigger thinks it’s a Cadillac,” Dundes told the Philadelphia Inquirer, which alerted the campaign and the Secret Service to the allegation.
   
Google Books
Car and Motorcycle Slang
By Lewis Poteet
Lincoln, NE: iUniverse.com, Inc.
2000
Pg. 152:
Pontiac —— Poor Old Negro Thinks It’s A Cadillac.
 
Urban Dictionary
Pontiac
Poor Old Nut Thinks Its A Car
by toolazyforname May 01, 2003
 
Urban Dictionary
pontiac
Poor old nigger thinks its a cadillac
Look at that black guy, he thinks he’s pimpin.
by The one October 16, 2003