TACA, the airline of El Salvador, was founded in 1931 and was originally from the acronym of Transportes Aéreos Centroamericanos. TACA has been nicknamed with the backronym (back acronym) “Take A Chance Again” since at least 1947, “Take A Chance Airline” since 1984 and “Take A Coffin Along” since 1985.
   
 
Wikipedia: TACA Airlines
TACA is the flag-carrier of El Salvador and trade name “brand” comprising a group of five independently IATA-coded and -owned Central American airlines, whose operations are combined to function as one and a number of other independently owned and IATA-coded regional airlines which code-share and feed the TACA brand system. TACA, originally an acronym of Transportes Aéreos Centroamericanos (Central American Air Transport), now stands for Transportes Aéreos del Continente Americano (Air Transport of the American Continent), reflecting its expansion to North, Central, South America and the Caribbean. However, the brand is going to disappear in 2013. The AviancaTaca Group has announced that all its subsidiaries will operate under the name of Avianca.
 
Google Books
American Notes & Queries
Volumes 7-8
1947
Pg. 90:
In Central America, for instance, the TACA is known, perhaps for reason, as “Take a chance again.”
Alfred E. Hamill
 
13 November 1984, Chicago (IL) Tribune, “Central America puts fear back in flying” by George de Lama, pg. 10:
There is TACA the Salvadoran airline. For us it is “Take a Chance Airline.”
 
Google News Archive
20 April 1985, The Citizen (Ottawa, Ontario), “Flying as casual as hopping a bus in San Miguel” by Eric Hamovitch (Southern News), pg. G6, col. 4:
Thus, TACA is said to stand for Take A Chance Airlines. Since all its flights pass through El Salvador, it could also mean Take A Coffin Along.
 
Google News Archive
2 January 1987, Calgary (Alberta) Herald, “South American airlines inspire gallows humor” by Mark Prendergast, pg. A5, col. 3:
TACA, the Salvadoran airline, has come to mean Take A Chance Airlines, or Take A Coffin Along.
 
27 August 1987, The Times (Trenton, NJ), “Central America: Nations in Turmoil” by Paul Sigmund and William Potter,  pg. 1, col. 1:
TEGUCIGALPA, Honduras—The longest 30-minute plane ride in Central America may be the flight from El Salvador to Tegucigalpa, the capital of Hunduras. Dealing with TACA (frequent flyers call it Take A Chance Airways) has something to do with it.
 
Google Books
Disposable Patriot:
Revelations of a Soldier in America’s Secret Wars
By Jack Terrell and Ron Martz
Washington, DC: National Press Books
1992
Pg. 57:
The airline itself, TACA, was more like a sky taxi servicing the small countries on a daily basis. Maybe that’s why many people who flew the national airline of El Salvador called it Take A Chance Airlines.
 
New York (NY) Times
INTERNATIONAL BUSINESS; A Home-Grown Giant Of Central America
By LARRY ROHTER
Published: April 15, 1998
(...)
For TACA—shorthand for Transportes Aereos Centro Americanos—that means more head-to-head competition with some of the giants of the industry on what could be less than favorable terms. As a relatively small carrier, the company benefits from neither the economies of scale nor the name recognition of United States rivals.
(...)
Less than two decades ago, amid wars in much of Central America, TACA International Airlines was a tiny carrier, with revenue of $18 million and initials that were said to stand for ‘‘take a chance airlines’’ because of its irregular schedule and suspect equipment.