“You Texas brush-popper!” said John Wayne in the movie True Grit (1969). A “brush popper” (also known as a brush buster, brush hand, brush rider, brush thumper and brush whacker) is a cowboy who works in brush country. The term dates to the 1920s, when it appears in the writings of Texas folklorist J. Frank Dobie.
 
A firearm called a “Texas Brush Popper” was trademarked in 2006.
   
     
Internet Movie Database
Plot summary for
True Grit (1969) 
The murder of her father sends a teenage tomboy, Mattie Ross (Kim Darby), on a mission of “justice”, which involves avenging her father’s death. She recruits a tough old marshal, “Rooster” Cogburn (John Wayne), because he has “grit”, and a reputation of getting the job done. The two are joined by a Texas Ranger, La Boeuf (Glen Campbell), who is looking for the same man (Jeff Corey) for a separate murder in Texas. Their odyssey takes them from Fort Smith, Arkansas, deep into the Indian Territory (present day Oklahoma) to find their man. Written by John Vogel {jlvogel@comcast.net} [edited]
(...)
Internet Movie Database - Memorable Quotes
[LeBoeuf is spanking Mattie]
Mattie Ross: Are you gonna let him do this?
Rooster Cogburn: I don’t believe I will. Drop that switch, LaBoeuf. Put it down, I said. You’re enjoying it too much.
LaBoeuf: You’ll find I go ahead with what I start.
Rooster Cogburn: [Rooster draws and cocks his pistol] You do and it’ll be the biggest mistake YOU ever made, you Texas brush-popper!
 
Wylie and the Wild West
A “brush popper” is a cowboy who hunts cattle in the brush. 
   
GunsAmerica
Cimmaron “Texas Brush Popper” 
SELLER NAME Legendary Guns
SELLER STOCK # L410-06
CATEGORY Cimmaron Rifles > Lever
CONDITION NIB.
Price:  $1,059.00
New from Cimmaron, 18 1/2 inch 1873, called the “Texas Brush Popper” I like it , a little nose heavy, but 10 1/2 inches Octogon and 8 inches round, Just the right length to use when moving thru brush, and scrubby tree’s.. Full length mag tube and crescent butt stock. 
 
(Dictionary of American Regional English)
brush popper n Also brush buster, brush hand, brush rider, brush thumper, brush whacker. West
A cowboy who works in brush country.
1929 Dobie Vaquero 207 TX, Sam was a brush popper. Like many another brush whacker, he was wont to emerge from a thicket with enough wood hanging in the fork of his saddle to cook a side of yearling ribs. Ibid 241, He was the best brush hand that I have ever known and he was a born horseman.
1945 Thorp Pardner 262 SW, Some of the riders on these mavericking roundups (“brush-poppers” as we used to call them) took a lot more chances than any other riders going.
1961 Adams Old-Time Cowhand214, The brush rider…was an expert at runnin’ cattle in the brush…[He} went by such names as “brush buster,” “brush thumper,” “brush hand,” “brush whacker,” and “brush popper,” the latter bein’ the most pop’lar title.

(Historical Dictionary of American Slang)
brush popper n. West. a cowboy who works in brushy country.
1928 Dobie Vaquero x: The story of the brush and the brush hand has never been written, though the cattle industry of America began in the mesquitals along the Rio Bravo, and the first cowboys were “brush poppers.” Ibid. 86 [ref. to late 19th C.]: Walton knew that I was a brush-popper and that I hankered for ranger service.
1934 Rhodes Beyond Desert 24: Listen, fellow, I’m no brush-popper.
1940 F. Hunt Trail From Tex. 27 [ref to ca1880]: I ain’t got much sense but I know better’n to wanta be a brush-popper.
1979 Decker Holdouts 35: I’m an arena cowboy. I’m no brush popper like you.
 
Google Books
Fifty Years on the Old Frontier:
As Cowboy, Hunter, Guide, Scout, and Ranchman
by James Henry Cook
New Haven, CT: Yale University Press
1923
Pg. 33:
...outfit of riders, or “brush-poppers,” as they were frequently called, we soon had a herd of about twenty-five hundred thrown together.
 
11 July 1926, Dallas (TX) Morning News, “Cowboys: Declared Strong, but Not Tough” by J. Frank Dobie, section 3, pg. 6:
This cowman used to be a “brush popper” in South Texas; then he went out on the plains and worked for big outfits.
 
26 November 1929, San Antonio (TX) Light, “Cowboy given honors by Dobie,” pg. 11B, col. 3:
“Unseen and unapplauded, the brush hand almost daily exerts as much skill and grit as any rodeo star ever displayed in conquering the most savage outlaw horse. Nobody ever sees the brush popper in action. A brush hand can work on the prairie as well as any prairie trained cowboy, but a prairie-trained cowboy is as helpless in bad brush as any tenderfoot.”
   
11 October 1931, San Antonio (TX) Light, part II, pg. 14?, col. 1:
...he considered himself second to no man in skill as a “brush popper.”
 
Google Books
Cowboy Lingo
by Ramon F. Adams
Boston, MA: Houghton Mifflin Co.
1936
Pg. 23:
... “where the brush was so thick a bird couldn’t fly through and snakes had to climb to see out,” was known as a “brush-hand,” “brush-popper,” “brush-thumper,” “brush-whacker,” “brush-buster,” or “limb-skinner.”
 
(Trademark)
Word Mark TEXAS BRUSH POPPER
Goods and Services IC 013. US 002 009. G & S: Firearms. FIRST USE: 20060130. FIRST USE IN COMMERCE: 20060130
Standard Characters Claimed
Mark Drawing Code (4) STANDARD CHARACTER MARK
Serial Number 78953859
Filing Date August 16, 2006
Current Filing Basis 1A
Original Filing Basis 1A
Published for Opposition January 1, 2008
Owner (APPLICANT) Cimarron Firearms Company, Inc. CORPORATION TEXAS 105 Winding Oaks Fredericksburg TEXAS 78624
Attorney of Record Mark Falkin
Disclaimer NO CLAIM IS MADE TO THE EXCLUSIVE RIGHT TO USE “TEXAS” APART FROM THE MARK AS SHOWN
Type of Mark TRADEMARK
Register PRINCIPAL
Live/Dead Indicator LIVE