“The history of tacos predates the arrival of Europeans in Mexico. Anthropological evidence shows the native people living in the lake region of the Valley of Mexico traditionally ate tacos filled with small fish.  At the time of the Spanish conquistadors, Bernal Diaz del Castillo, documented the first taco feast enjoyed by Europeans. Hernan Cortes arranged this meal for his captains in Coyoacan. It is unclear why the Spanish used the word taco to describe this native food. One suggested origin is the word ataco, meaning stuff or to stuff.”

https://nationaldaycalendar.com/national-taco-day-october-4/