Quesadilla

Quesadillas are an important part of Tex-Mex cuisine. A quesadilla is a turnover with filling, such as beans, cheese, rice, and beef or chicken. The Gebhardt Chili Powder Company of San Antonio has the “quesadilla” in its cookbooks from at least 1911.
     
 
Wikipedia: Quesadilla
A quesadilla (IPA [kesa’ðiʝa], usually anglicized as [ˌkeɪsʌ‘diːjʌ]) is a Mexican snack food made of cheese (and occasionally other ingredients) on a folded corn tortilla and cooked until the cheesse melts. The word comes from Spanish, and literally means “little cheesy thing” or “cheesy” (from queso, or “cheese”, + ada, an adjectival suffix, + illa, a diminutive suffix).

In other countries, quesadillas may be an unrelated cheese-based food.
 
Ingredients
Exactly what constitutes a quesadilla varies from region to region and between the U.S. and Mexico and is not universally agreed upon by chefs. However, it is generally agreed that the quesadilla is cooked after being filled or stuffed with the cheese. Variations in which the quesadilla is stuffed with aditional ingredients sometimes are incorrectly named burritos, while a taco or burrito is filled with pre-cooked ingredients as do some variations of the quesadilla, the additions are mostly diferent. Also, the quesadilla is folded and not wrapped.
 
The purist faction may argue that only the folded-style Mexican version is a “real” quesadilla, although some chefs such as Rick Bayless have made more liberal “interpretations.”
 
Also, there is the American naming of quesadilla not just to the folded Mexican “quesadilla” but to the Mexican “sincronizada”.
   
Merriam-Webster Dictionary
Main Entry: que·sa·dil·la
Pronunciation: \ˌkā-sə-ˈdē-ə also -ˈthē- or -ˈthēl-yə\
Function: noun
Etymology: Mexican Spanish, from Spanish, cheese pastry, diminutive of quesada, from queso cheese, from Latin caseus
Date: 1935
: a tortilla filled with a savory mixture, folded, and usually fried
   
(Oxford English Dictionary)
quesadilla
[Sp.] 
A variety of turnover, usu. with a cheese filling.
1944 E. ZELAYETA Elena’s Famous Mexican & Sp. Recipes iv. 35 Quesadilla. Tortilla Stuffed with Cheese. Take fresh tortillas..place generous piece of Monterey cream cheese..in the center, and fold it over as you would a turnover… Cook lightly, turning often until cheese is melted.
       
New York Public Library catalog
Author Blanquel, Simón. 
Title Novisimo arte de cocina
Nueva cocinera mexicana, ó, excelente coleccion de las mejores recetas : para que al menor costo posible, y con la mayor comodidad, pueda guisarse á la española, francesa, italiana é inglesa, sin omitirse cosa alguna de lo hasta aquí publicado para sazonar al estilo de México : lleva añadido lo mas selecto que se encuentra acerca de la repostería; el art de trinchar &c. ... 
Imprint México: Impreso por Luis Heredia, 1841.
Pg. 107: 
Quesadillas de regalo.
 
Google Books
One Hundred & One Mexican Dishes
compiled by May E. Southworth
San Francisco, CA; Paul Elder and Company
1906
Pg. 62:
QUESADILLAS
MAKE thin corn-meal pancakes six inches across. Dip one in hot chile sauce, lay on a plate and cover with raw onion chopped fine, grated cheese and stoned olives cut in half. Lay on this six other pancakes, each dipped in the chile sauce and covered with the onion, cheese and olives. Pour the remaining sauce over the top and set in a hot oven for a few minutes. Serve hot, cutting like layer-cake.
   
Mexican Cooking
Gebhardt Chili Powder Co.
San Antonio, Texas
1911
Pg. 36:
Quesadilla Mexicana—Mexican Rarebit
Use one pound of rich, mild cheese grated, one tablespoonful of butter, one egg, one-half cupful of stale beer or milk if preferred, a pinch of salt and from one to two heaping tablespoonsful of Gebhardt’s Eagle Chili Powder.  First, put the butter in a sauce pan and when melted add the Eagle Chili Powder and salt, stirring until thoroughly mixed; add the cheese and continue to stir briskly until it is thoroughly melted; then slowly add the beer or milk, stirring all the time, and lastly add the egg and stir until the rarebit begins to thicken.  Serve quickly on crackers or preferably on hot toast, being sure that your platters are hot.
 
Terry’ Guide to Mexico
by T. Philip Terry
Revised Edition
Boston and New York: Houghton Mifflin Company
1935
(The copyrights on the book read “1909, 1922, 1927, and 1935”—ed.)
Pg. 244d:
QUESADILLAS are tortillas filled with various bits of meat and vegetables and
fried in lard.
 
Cooking South of the Rio Grande
by George Luther Nelson
San Antonio: Neolon Sales Service
1935
Pg. 27:
Quesadillas
1 dozen tortillas
1 lb. white cheese (grated)
Place grated cheese on tortilla and wrap, fastening with a tooth pick; place in a hot oven without fire until cheese melts and pour over tortilla when removed from oven, a hot sauce to suit taste.
 
Your Mexican Kitchen:
A Compilation of Mexican Recipes Practicalbe in the United States
by Natalie V. Scott
New York: G.P. Putnam’s Sons
1935
Pg. 5:  QUESADILLAS DE CARNE (OF MEAT)
Pg. 6:  QUESADILLAS DE QUESO (OF CHEESE) (...) QUESADILLAS OF SQUASH FLOWERS
 
26 October 1938, Los Angeles Times, pg. B9:
Honduras Rice Cake
(Quesadilla de Arroz)