“Gubberment” has been a black dialect word for “government” since at least 1813. “Gubbermint” has been cited in print since at least 1925. “Gubberment/gubbermint” has seen increased usage in the computer age as a mock name for the government.
 
Dialect variations of the word “government” include “gubment/gubmint” (from the 1800s) and “gooberment/goobermint” (from the late 1900s).
   
 
Wiktionary: gubberment
Noun
gubberment (plural not attested)
1. (dialect, nonstandard) government
 
Urban Dictionary
gubberment
Southern slang word for Government
Damn Gubberment revenuers
by hillsurfer Mar 24, 2007
 
Urban Dictionary
Gubbermint
Stupid, slack-jawed government
Farmer: Mah crops ain’t workin no mo anymo! Stoopid gubbermint!
by Ajbdtc826 Jul 6, 2010
 
2 March 1813, New Jersey Journal (Elizabethtown, NJ), pg. 4, col. 2:

—(...) I fraid de old toger himself take him from dat great tage, where he trut and tromp and buse de gubberment.
   
Google Books
Narrative of an exploring voyage up the rivers Kwóra and Bínue: (commonly known as the Niger and Tsadda) in 1854
By William Balfour Baikie
London: John Murray
1856
Pg. 334:
“Why,” said he in his peculiar way, and pointing to a print of Buonaparte, ” why your gubberment keep me here, I no do bad like he, I be free man, I be King.”
     
Google Books
March 1863, Southern Literary Messenger, pg. 148:
De Yankees says de cullud poplation ought to rule, but de Dixies wont gib em up, so de Yankees is to whip de Dixies and gib de gubberment to de cullud poplation for de next hunderd years, and den de^rhit* folks dey come in agin.
 
Google Books
Four Years of Fighting
By Charles Carleton Coffin
Boston, MA: Tickner & Friends
1866
Pg. 233:
“Jes let gubberment pay me, boss, and see if I can’t.”
 
Google Books
Across Unknown Australia
By Michael Terry
London: H. Jenkins Ltd.
1925
Pg. 19:
Some day their efforts come before the notice of the ” big-feller Gubbermint.”