Thinking of tacos, what type of meat is used in tacos de pescado?
And the answer is: fish.
In Mexican cuisine, tacos can be made with a hard fried corn tortilla, or with a soft flour tortilla in Mexican-American cuisine. Tacos de pescado are filled with fish, and most likely originated in the Mexican state of Baja California, on the Pacific coast. (OK, now we're hungry!)
The term "tacos" is a relatively new one – its first reference can be traced to 18th century gunpowder charges in Mexican silver mines. Following its explosive beginnings, it wasn't until Mexican migrants began arriving in the U.S. that tacos as the delicious tortilla-meat combination began to be known and enjoyed by the public. Following World War II, the second generation of Mexican migrants began to adapt traditional Mexican food to the ingredients that were available through the U.S. food-processing industry. For example, hamburger meat was exchanged for offal meat, while cheddar cheese, iceberg lettuce, and tomato were introduced. At the same time, immigrants flowing into Mexico began to adapt and add on to traditional flavors in their own right, such as pineapple and pork.
Standardized forms of tacos such as Glen Bell's Taco Bell restaurants directly draw from Mexican tradition to create a distinctly Americanized fast food franchise. While Mexican cookbooks in the 1940s coined the U-shape, hard tortilla shell, Glen Bell laid claim to its popularization.
Check out this Smithsonian article for more on the history, popularization, and Americanization of this dinnertime staple.