The Border Patrol on the United States-Mexican border have called a (usually illegal) immigrant not from Mexico as an “OTM,” or “Other Than Mexican.” OTMs have usually been from Central America and South America, but in the 2000s, even Iraqis coming across the border were called “OTMs.”
   
“OTM” has been cited in print since at least 1977.
     
   
Urban Dictionary
otm
Other Than Mexicans A term used by US Border Patrol agents when catching illegal aliens.
What a night last night! We caught 250 people 23 of them were OTMs
by abula Feb 29, 2004
   
21 August 1977, Valley News (Van Nuys, CA), Inside magazine, pg. 3, col. 2:
Aliens from Mexico pay $200 to $350 each to be smuggled into the United States. Persons other than Mexican (OTMS) usually from Central and South America, may pay up to $1,600 each, depending upon the point of origin and the destination.
(“OTMS” appears to be an editing error. See the same story in the citation below—ed.)
   
25 August 1977, Austin (MN) Daily Herald, “Illegal aliens: American dilemma” by Steve Kline, pg. 7, col. 2:
Aliens from Mexico pay $200 to $350 each to be smuggled into the United States. Persons other than Mexicans (OTMs) are usually from Central and South America; they may pay up to $1,600 each, depending upon the point of origin and the destination.
 
7 July 1980, New York (NY) Times, “Number of Alien Arrests Falls as Border Patrol Is Stretched Thin” by John M. Crewdson, pg. A12:
Mr. Walsh added that the increasing number of aliens flowing across the border were what the Border Patrol calls “OTM’s,” for “other than Mexican.” These tend to come from the “troubled triangle”—the countries of Nicaragua, Guatemala and El Salvador, all of which has undergone recent political upheaval—and generally enter the country with the aid of one of the burgeoning number of illicit organizations engaged in the criminal smuggling of aliens, he said.
   
21 July 1980, New York (NY) Times, “Smugglers Find Aliens As Valuable as Drugs Along Mexican Border” by John M. Crewdson, pg. A10:
For aliens known to the Border Patrol as “OTM,” or “other than Mexican,” the first contact with a smuggler usually comes in the homeland they are preparing to flee, and contacts are not difficult to make.
 
Google Books
Another Land
By Richard Vasquez
New York, NY: Avon
1982
Pg. 12:
“They’re among the IAs you officially classify as OTM’s — Other Than Mexican.”
(“IA” = illegial alien—ed.)
 
Google Books
Journal of Contemporary Studies
v. 6 - 1983
Pg. 50:
In addition, too many apprehensions of OTM (other than Mexican) aliens can create severe pressures on immigration courts that are already heavily burdened in some districts.
 
Google Books
In Liberty’s Shadow:
Illegal aliens and immigration law enforcement
By Edwin Harwood
Stanford, CA: Hoover Institution Press, Stanford University
1986
Pg. 9:
“Most deportable overseas aliens, who are referred to in INS jargon as other-than-Mexican (OTM) aliens, enter legally as students or visitors but subsequently violate the conditions of their visas by working without authorization or overstaying.”
 
Google Books
The Vanishing Border:
A photographic journey along our frontier with Mexico
By Brent K. Ashabranner and Paul Conklin
New York, NY: Dodd, Mead
1987
Pg. 17:
OTM is Border Patrol shorthand for Other Than Mexican. The great majority of OTMs are from El Salvador, Guatemala, and Nicaragua.
       
Google Books
The militarization of the U.S-Mexico border, 1978-1992:
Low intensity conflict doctrine comes home
By Timothy J Dunn
Austin, TX: CMAS Books, University of Texas at Austin
1997
Pg. 79:
One notable subcategory of the overall data on apprehensions was “other than Mexican” undocumented immigrants (or “OTMs,” in INS lingo).
 
Google Books
U.S.-Mexico borderlands issues:
The bi-national boundary, immigration, and economic policies
By Ellwyn R Stoddard
El Paso, TX (747 Camino Real, El Paso 79922): The Promontory
2001
Pg. 232:
OTM (Other Than Mexican) illegals
   
Sherdog Mixed Martial Arts Forums
LavrentiBeria
07-17-2007, 04:41 PM
Border agents call them OTM (other than mexican)
The FBI is investigating an alleged human smuggling operation based in Chaparral, N.M., that agents say is bringing “Iraqis and other Middle Eastern” individuals across the Rio Grande from Mexico.
 
An FBI intelligence report distributed by the Washington, D.C. Joint Terrorism Task Force, obtained by the Blotter on ABCNews.com, says the illegal ring has been bringing Iraqis across the border illegally for more than a year.