The “Hook ‘Em Horns” hand gesture (with index finger and pinkie standing up as “horns”) was invented by then-University of Texas head cheerleader Harley Clark at a Longhorns pep rally in 1955.
 
However, the pre-1955 origin of the phrase “Hook ‘Em Horns” is unclear. A “Hook ‘Em Cows” tradition seems to have been popular at the University of Minnesota through the 1930s. (Surprising, since the Minnesota mascot is the golden gopher. “Hook ‘Em Cow” began at the South St. Paul stockyards.) A Texas basketball team in the 1930s was also called “Hook ‘Em Cows.”
 
 
Texas Football
Hook’em Horns
University of Texas at Austin cheerleader Harley Clark knew what he was going to teach football fans at a 1955 pep rally was going to catch on faster than poodle skirts and leather jackets. It had to. After all, the Texas A&M Aggies’ “Gig ‘em” gesture had been around for years.
 
Clark sold the student body on the symbolic approximation of the horns of Longhorn mascot Bevo and, thus, began the “Hook ‘em Horns” hand signal.
 
The salute quickly took its place beside the university traditions of singing The Eyes of Texas and lighting the Tower orange.
 
Fellow student Henry Pitts, who had come up with the Longhorn sign during an inspired game of shadow casting, had shown Clark the sign three days before the Texas Christian University game.
 
At the Gregory Gym pep rally for that game, Clark showed everyone how to make the Horns hand sign and then proclaimed it to be used from that time forward. By the thousands, the university faithful extended their pinkies and index fingers toward heaven.
 
“A lot of my friends thought it would be too corny, but I thought it was perfect,” said Clark in a recent interview. “Everyone walked out of Gregory Gym that night crazy with it.”
 
The next day at the game, Clark watched the “Hook ‘em Horns” gesture surge around the stadium from one side to the other. “TCU had a fine team,” he said. “We had to make up in spirit what we lacked on the football field.”
 
In the mid-1950s, Clark was head cheerleader at the university, a position that was elected by the student body.

“It was second only in importance to the Texas governor,” he laughed. “I loved the university so much I stayed for nine years (earning undergraduate and master’s degrees in government and a law degree).”
   
Wikipedia: Hook ‘em Horns
Hook ‘em Horns is the slogan and hand signal of The University of Texas at Austin. Students and alumni of the University employ a greeting consisting of the phrase “Hook ‘em” or “Hook ‘em Horns” and also use the phrase as a parting good-bye or as the closing line in a letter or story.
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History
Harley Clark introduced the Hook ‘em Horns sign in 1955. Clark was head cheerleader at the university, a position that was elected by the student body. “It was second only in importance to the Texas governor,” he jokes. Clark got the idea for the hand-sign from his colleague Henry Pitts, who had been casting shadows on the wall at the Texas Union. Clark showed an enthusiastic student body the sign a few nights later at a football pep rally at Gregory Gym. According to Neal Spelce, who attended the rally when he was a student at the University, “a lot of people didn’t get it right at first,” but it caught on rapidly from there. By the thousands, students extended an arm to create the now famous salute. The next day, at the Texas Longhorn vs. TCU football game, Clark stood in awe as the “Hook ‘em Horns” hand sign surged from one side of the stadium to the other.
     
eBay   
WE’RE THERE
“WITH BELLS ON”
SOUTH ST. PAUL
HOOK ‘EM COWS
UNION STOCK YARDS
(A pin—ed.) 
 
16 October 1925, The Daily Texan (Austin, TX), pg. 3, col. 6:
Hook ’em, Longhorns!

Time Magazine 
Football
Posted Monday, Nov. 26, 1934
The “Hook ‘Em Cows” are affluent, football-mad livestock commission merchants and packers of the Twin Cities. Since Stan Kostka comes from a little farm near South St. Paul, the stockyard centre of Minnesota, and has two brothers working in the stockyards, he has a natural claim to “Hook ‘Em Cow” loyalty. 
 
23 January 1935, Brainerd (MN) Daily Dispatch, pg. 5, col. 3:
The “Hook “Em Cows,” strong touring basketball team from Athens, Texas, will provide the opposition for the Russell Dodgers, powerful local independent quintet, here Friday at the Franklin Junior high school.
   
The Hook ‘Em Cows, composed of former college stars, have been playing together for three years and their record boasts victories over the strong independent and college quintets in the country.
   
25 November 1936, Bismarck (ND) Tribune, pg. 2, col. 4:
MINNESOTA’S FIRST
“YELL” KING KILLED
   
Famed “Hook “Em Cow” Rooter,
Dr. John Campbell, Dies
in Auto Upset.
 
South St. Paul, Minn,, Nov. 25—(AP)—Three men, including Dr. John E. Campbell of South St. Paul, famed “Hook ‘Em Cow” rooter at University of Minnesota football games, were killed in two automobile accidents on Highway 55 near Hastings Tuesday night.
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The doctor was the first Rooter King at the University of Minnesota in 1894. During the past 42 years, he held the record of never having missed a home football game.
   
Time Magazine
“Hook ‘Em Cow”
Posted Monday, Feb. 8, 1937
Not since most of them were youngsters, 20 years ago, had the members of South St. Paul’s old “Hook ‘Em Cow Club” had such a night to sing their song.
   
11 September 1941, Panola Watchman (Carthage, TX), pg. 3, col. 2:
He is a major factor behind the unique “Hook ‘Em Cows,” a fun organization of the men of the South St. Paul Stockyards, which has a uniformed drum and bugle corps and a troop of 40 horsemen, both units being much in evidence in all parades.
 
27 November 1952, The Daily Texan (Austin, TX), pg. 1, right masthead:
Hook ‘em, Horns
Pg. 3, col. 7 ad:
Hook ‘Em
HORNS
(Fidelity State Bank.—ed.)
 
29 November 1955, The Daily Texan (Austin, TX), “Fifteen Close Careers With WIn Over Aggies” by Clark Carpenter, pg. 3, col. 2:
One boy took a red candle into the stands with him and when the Aggies kicked off, one hand was raised in the gesture of “Hook em Horns” while the other held a burning red candle.
 
21 September 1958, The Daily Texan (Austin, TX), pg. 3, col. 3 photo caption (with hand gesture shown):
Freshmen Yell Their First ‘Hook ‘em Horns’
 
14 November 1959, The Daily Texan (Austin, TX), “‘Horns Exhibit Determination Before 3,000 Chilled Rooters” by Charlie Smith, pg. 1, col. 3:
As they assembled, members of the Delta Sigma Phi fraternity joined the group by marching in the cold north wind from West 24th Street with two giant sign. One carried the message “Hook the Horny Toads.” The other was a large hand with the index and little fingers up indicating, “Hook ’em. Horns.” In the middle of the “hand” was painted ‘‘Beat TCU.”
 
15 September 1961, The Daily Texan (Austin, TX), “Three Easy Steps To “Hook ‘Em ‘Horns” by Billy Pumphrey, pg. 10, cols. 4-5:
1. Fold your middle two fingers in the palm of your hand and fold your thumb over them. Leave your index finger and your little finger projecting outward forming the silhouette of a longhorn.
2. Extend your arm straight above your heador pointed at the opposing team, shaking handlike the head of a charging bull.
3. Now yell: “Hook ‘em ‘Horns!”