The coyote is an animal seen in the Southwest; J. Frank Dobie’s The Voice of the Coyote (1949) tells of the folklore of the coyote. Smugglers of aliens (Mexicans and other nationalities) into the United States from Mexico have been called “coyotes” or “wolves of the border” since at least 1923. The 1918 silent film Wolves of the Border might have influenced both terms.
     
 
Wikipedia: People smuggling
People smuggling is a term which is used to describe transportation of people across international borders to a non-official entry point of a destination country for a variety of reasons. Typically those being transported may not have adequate formal travel documents or prior approval to enter the destination country.
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In the Southwest United States, a “coyote” is a person paid to smuggle illegal immigrants across the border between Mexico and the United States. Snakeheads are smugglers from China who smuggle people into the United States and other Western countries.
   
Internet Movie Database
Wolves of the Border (1918)
Director: Clifford Smith
Writer: Alan James
Release Date: 12 May 1918 (USA) more
Genre: Western
Plot Synopsis: This plot synopsis is empty. Add a synopsis
Plot Keywords: Cowboy / Kidnapping / Rancher / Rescue
 
Internet Movie Database
Wolves of the Border (1923)
Director: Alan James
Release Date: 15 January 1923 (USA) more
Genre: Western / Comedy / Drama
   
(Oxford English Dictionary)
coyote, n.
Zool. The name, in Mexico and now in the United States, of the prairie- or barking-wolf (Canis latrans) of the Pacific slope of North America.
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U.S. slang. A person hired to assist people in illegally crossing the border from Mexico into the United States.
1924 Los Angeles Times 4 June I. 12/7 There has been..the immigration service says, a band of criminals on this border, known as ‘coyotes’, who live by preying upon persons wishing to secure an easy entrance to the United States.
1943 Econ. Geogr. 19 359/2 The facilitators of illegal entrance, the smugglers or ‘coyotes’, the contractors or ‘engachistas’ who provided peons with jobs over the border.
1972 Los Angeles Times 17 Sept. (West Mag. section) 19/3 The coyote took us by way of Tecate in a station wagon… He let us out on the highway and we waited there..to lose the border patrol.
   
(Historical Dictionary of American Slang)
coyote n.
Police. S.W. a labor contractor or other person who brings illegal immigrants into the U.S. from Mexico.
1929 Gill Und. Slang: Coyotes—Labor agents.
1970 S. Steiner La Raza 300: “Coyote!” is what the campesinos say of a man like Corrilio Macias.
1973 U.S. News & W.R. (July 23) 32: Smugglers, known as “coyotes” in the Mexican-American community in Los Angeles.
1974 Martinez & Longeaux y Vasquez La Raza 127: A worker in Mexico would be picked up by a labor smuggler—called a coyote.
1977 L.A. Times (Jan. 15) II 5: His name was Roberto and he paid a “coyote” 300 American dollars to smuggle him across the border.
     
24 May 1923, Galveston (TX) Daily News, “Border Bandits Commit Many Murders: Immigration Inspector Says Recent Killing of Italians One of Many Similar Crimes,” pg. 1, col. 8:
A new race has sprung up on the Mexican side of the border, referred to often as the “wolves of the border.” The greed for gold has got their blood aflame, and their prey is the simple European alien who wishes to make his home in America but is unable to comply with the immigration standards.
 
ONE VICTIM ESCAPES.
The recent murder of six Italians, who bartered for their passage across the Rio Grande only to be betrayed and shot down by their guides and robbed of their money, is believed to be only one of a series of wholesale murders the bandit smugglers have committed.
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Captain Hanson, who has just returned from the border, believed that hundres of unsuspecting Europeans have met similar fates. The characters of the “coyotes” at the border are the lowest and “the murder of a fellow man means nothing to them,”: he said.
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Says Guides Are Coyotes.
The “coyotes,” as Captain Hanson refers to the guides, then return to take another party and if any questions are asked they simply state that the party has been safely carried across the river, with no one to deny their statement.
 
27 June 1923, San Antonio (TX) Express, “Scores of Mexicans Use Others’ Head Tax Receipts to Enter United States,” pg. 1, col. 2:
Reports from Laredo Tuesday also told of the arrest of one German alien who claimed to have been robbed by “coyotes,” the Mexican nickname for those who smuggle aliens across the river, the German charging that $150 had been taken from him.
(...) (Col. 3—ed.)
He explained that the alien passes through the hands of about five “coyotes” before he reaches the American side of the river and ultimately falls into the hands of government officers who place him in jail for deportation.
   
11 January 1924, New Castle (PA) News, pg. 2, col. 6:
With legal entrance of aliens practically cut off until June 30 the border “coyotes” a smugglers term for a criminal class which preys upon foreigners anxious to enter this country are becoming more active in piloting an undesirable class over the Mexican border, according to official reports.
   
19 January 1948, Dallas (TX) Morning News, “More Talk About Coyotes” by J. Frank Dobie, section I, pg. 13:
In Mexican popular speech, coyote means: a pettifogger, a thief, any kind of shyster or go-between, a curbstone broker, a fixer who has “pull” to sell, an oil or mining scout with “practical experience” in selling leases, also the respectable Minister of Mines, a drink of mixed beer and brandy. As Lumholtz puts it, “the regard that the Indians have for their Mexican masters is shown in the name by which they refer to them—coyotes.”
 
Use in Southwestern States.
On the border, a smuggler of aliens is called a coyote-enganchista. In the interior of Texas a certain kind of agent, often a jackleg lawyer, who hangs around court houses and charges ignorant Mexicans outrageous fees for services as commonplace as getting a notary public’s certification is called a coyote. He is often a Mexican himself. In New Mexico, the name, among other meanings, denotes a half-breed—a mixture of Anglo and Hispano bloods or of Caucasian and Indian—who is loyal to neither line. Mexicans call bastard children coyotitos. Without aspersion they call also the last child in a family a coyotito. In the folklore of ignorance—and not all folklore by any means springs from ignorance—the coyote is a cross between lobo and fox.
 
Google Books
The Voice of the Coyote
by J. Frank Dobie
Boston, MA: Little, Brown
1949
Pg. 258:
On the border, a smuggler-over of aliens is called a coyote enganchista.
 
10 April 1977, Dallas (TX) Morning News, “INS nominee appears capable for job,” section A, pg. 11:
“We need tougher laws on the smugglers, the coyotes, the guys who smuggle people. They smuggle people and the penalties we assess are relatively light.”