Wetback (Wet Back)

“Wetback” (or “wet back”) is a derisive slang term for a Mexican (who crosses the Rio Grande into Texas and has a “wet back”). The term has been used from at least 1920 and is considered a racial epithet.
 
 
(Oxford English Dictionary)
wetback orig. and chiefly U.S., an illegal immigrant who crossed the Rio Grande from Mexico to the U.S.; also attrib. and transf.
1929 Foreign Affairs Oct. 101 The peon walks or swims across..and is welcomed by his countrymen here as a ‘*wet back’.
1972 Observer (Colour Suppl.) 28 May 28/1 Last year in California alone, border patrols turned back 27,000 wetbacks (the contemptuous name derives from their practice of swimming the Rio Grande to reach the US).
1978 N.Y. Times Mag. 23 July 23/2 Wetbacks (a derogation of Mexicans swimming the Rio Grande to slip into the U.S.) became illegal aliens, and are now referred to as undocumented persons.
 
27 January 1920, Dallas (TX) Morning News, pg. 3:
The committee was told of instances where planters could not obtain laborers under the contract system permitted by the Labor Department and deals were made by them with Mexicans who furnished “wet backs.” This term applied to Mexicans brought across the river at points where there were no immigration inspectors and delivered in parties of 100 or more at a stated charge per head. They were then sent to the plantations and worked unmolested throughout the season. The planter would deduct from the Mexican’s pay the cost of getting him over and to the farm, an arrangement to which the laborer always agreed. After the season the Mexicans returned to Mexico with their accumulated earnings to live them up until the next season opened.
 
15 February 1920, Galveston (TX) Daily News, pg. 12, col. 5:
HOW “WETBACKS” ARE
SECURED ON BORDER
 
WITNESS TELLS OF WAYS LABOR IS
OBTAINED FROM MEXICO BY
TEXAS LANDLORDS.
 
Washington, Feb. 14.—Congress was introduced to a brand new term when a witness before a House immigration committee, discussing the Hudspeth resolution to admit Mexican labor for agricultural purposes, told how the Texas land owners secured “wet backs.”  These are Mexicans brought across the border at points where there are no immigration inspectors, without payment of the $8 head tax or standing the literacy test. They are supposed to have swam the Rio Grande, and their backs are still wet when they reach the plantation.
       
20 June 1920, New York (NY) Times, pg. XX6:
In the Laredo district alone, a speaker at a business men’s dinner recently estimated that between 10,000 and 15,000 of these “wetbacks,” as they are called because of their method of entry, had crossed into Texas in that time.
 
21 October 1920, Kansas City (MO) Times, pg. 12:
“Wet backs,” being Mexicans who swim the Rio Grande, are in high demand, but immigrant labor, entering the country by the front door is much more desirable, because it settles where it lights.
     
1 July 1923, Dallas (TX) Morning News, pg. 14, col. 1:
Information coming from inspectors show many coming over are of the wet-back class, or a Mexican who has waded the Rio Grande, thus avoiding head tax, literacy test, and other restrictions of the law.
 
5 December 1928, Dallas (TX) Morning News, part 2, pg. 18, col. 3:
A few of the laborers become “wetbacks,” perhaps, and do not return to Mexico, just as a few of them turn out to be lawless and troublesome.
 
21 June 1944, Valley Morning Star (Harlingen, TX), pg. 2: 
One such incident occurred at McAllen Monday, officers said, when a group of about forty “wetbacks” presented themselves to the authorities and asked to be sent back across the border.
 
23 June 1944, Valley Morning Star (Harlingen, TX), pg. 4:
Regarding the deportation of the thousands of wetbacks from the Rio Grande Valley district I think it’s the best thing that could be done for both labor and capital of American, because it should cause the “New Deal” to establish its largess programs which harbor and maintain many citizens in semi-idleness while our producers have to seek this cheaper foreign labor in order to continue in business.
 
9 March 1947, Los Angeles (CA) Times, pg. 7:
WASHINGTON, March 8. (AP)—California Congressmen today urged the Immigration Service to be lenient with Mexican “wetbacks” pending ratification of a new contract with Mexico for the importation of farm workers. “Wetbacks” are those Mexicans who enter the United States illegally, presumably by swimming the Rio Grande.
 
4 April 1948, Washington (DC) Post, “‘Wetback’ Play a Losing Game,” pg. B8:
The base-line of the game in Texas is the Rio Grande, which forms a 1000-mile border between El Paso and Brownsville. Some of the hiders swim or wade the shallow, narrow river. Because of that, all illegal Mexican immigrants have come to be known as “wetbacks.”
 
3 March 1951, Chicago (IL) Daily Tribune, pg. 7:
A “flying squad” of the AFL National Farm labor union today forced the deportation of 115 “wetback” Mexican farm laborers [illegal entrants] just as their presence in the United States, according to union officers, was being legitimized in an unlawful processing operation.