National Taco Day was celebrated on Oct. 4 and may be in our rearview mirror, but it’s never a bad day to have tacos, even if it’s not Tuesday.

I think most Americans agree with me, since we consume billions of them each year.

But how has such a seemingly simple food become so beloved, not just in Mexico, where it originated, or the U.S., where it was first imported, but around the world?

Perhaps it’s because these scrumptious packets of goodness can be filled with so many things — all kinds of meat, beans of all types, or even with vegetables like mushrooms or sweet potatoes as the star.

Aaron Sanchez, chef and television personality, has said, “Tacos are one of those dishes that are so iconic yet have such a large range of techniques and ingredients from region to region. Even just the difference between flour and corn tortillas is important. The main components to any taco are a tortilla, a filling, and a salsa. The varieties are virtually endless.”

You might say the secret to a good taco lies in getting those three components right. Perhaps tacos aren’t so simple after all.

It’s hard to pinpoint the exact origin of the taco, and conflicting theories as to their provenance exist.

History professor and author Jeffrey Pilcher has spent 20 years investigating the origins of Mexican food. His theory is that tacos originated with 18th century silver miners in Mexico.

The explosive charges used by these miners to excavate ore — small pieces of paper wrapped around gunpowder and tucked in holes to explode in the rock wall — were called tacos.

His theory gains traction when we learn that tacos were described as “tacos de minero,” or miner’s tacos, in the first reference to tacos as a food in an archive or dictionary a century later.

If this origin story is true, then culinarily speaking, tacos are a relatively recent addition to the food spectrum.

In contrast to Pilcher’s theory, others say tacos are much older than that, going back to when the Aztecs used corn tortillas as a sort of spoon to scoop up fillings like fish or offal (organ meats). This would put their origin somewhere between 500 to 1,000 B.C.

In addition, it’s possible that the word taco is not derived from explosive mine charges, but rather a Nahuatl, or Aztec language, word. “Tlahco” in that tongue means “half” or “in the middle,” and is perhaps a reference to the way tacos were formed.

According to Gustavo Arellano, who wrote “Taco USA: How Mexican Food Conquered America,” tacos have existed since there was a tortilla, even if they didn’t exist by that name.

“The earliest mention of taco as a food dates only to the late 19th century,” he says. “Previously, the word stood for anything from a pool cue to a hammer to getting drunk.”

Or, apparently, an explosive in a silver mine.

Thankfully, this paradox of the taco’s origin doesn’t diminish their deliciousness.

The first mention of the taco in the U.S. was in a 1905 newspaper. This was a time when immigrants from Mexico were beginning to come to the U.S. for work in mines, railroads and other similar jobs, and they brought their food traditions with them.

Mexican food in those days was often sold in pushcarts on the street, and since tacos were highly portable and cheap, they were a popular option.

Tacos started to become a more mainstream food when the children of immigrants rose in economic status. Mexican American tacos often were adapted to what was available in the American market — ground beef or chicken instead of offal, cheddar cheese, iceberg lettuce, tomatoes, and the like.

The first taco truck in the U.S. (and quite possibly the first food truck of any type) is believed to have been opened by Raul Martinez, a Mexican immigrant, who repurposed an old ice cream truck in 1974.

He parked his mobile taco eatery outside an East Los Angeles bar and was so successful that within six months he was able to leave the truck behind and open a restaurant. The restaurant, King Taco, now has 22 locations in California.

At the same time that Mexican immigrants were arriving in the U.S. early in the last century, Mexico was having an influx of immigrants, and their food traditions had an influence on what fills a taco.

For example, Lebanese migrants brought shawarma or gyro with them — lamb cooked on vertical spits served in pita bread. When they began to put the meat into tortillas, “tacos arabes,” or Arab tacos, were born.

Second-generation Lebanese immigrants changed the recipe a bit, using pork instead of lamb and serving it with pineapple. Tacos al pastor, which is pork sliced thin and served in a taco with pineapple, onion, and cilantro, is an adaptation of this Lebanese fare and is now considered a standard Mexican taco.

Glen Bell, the founder of Taco Bell, capitalized on the popularity of the taco. He originally owned a few hamburger joints but noticed how popular Mexican food was with non-Mexicans. He opened the first Taco Bell in 1962.

In his autobiography, Bell claimed he invented the hard-shell taco in the 1950s, which allowed for selling tacos in a fast-food style.

The “taco shell” could be made ahead of time in large quantities to store until they were needed, streamlining operations, in contrast to tacos that were made to order in Mexican restaurants with tortillas made fresh.

Despite Bell’s claims, the U.S. patent office shows records of patents for hard-shell tacos granted to Mexican restaurants in the 1940s, not to Bell. Also, Mexican cookbooks from the 1940s offered recipes for making them.

Tacos made with hard shells are known as “tacos dorado” in Mexican cooking. It’s unclear when the hard shells were first used, but it was at least a decade before Bell claimed to have invented them.

Tacos have become quite popular throughout the world. In Norway, for example, a communal make-your-own-taco night is celebrated each week. Instead of Taco Tuesday, Norwegians celebrate “Fredagstaco,” which takes place on Fridays.

Nearly 10% of the population of Norway participates in this food ritual.

There are endless variations on the taco. Middletown Pomo elder Millie Simon recalls eating fry bread filled with beans or meat while growing up. These are now known as Indian tacos.

I fell in love with fish tacos when introduced to them by my brother-in-law, a chef. Though I rarely eat meat, I’m still a huge fish taco fan and I enjoy sampling them in various locations.

Fish tacos also have dueling origin stories.

The city of Ensenada, Mexico is situated on the Pacific coastline in Baja California about 78 miles south of San Diego. In addition to being known for Mexican wine and American tourism, the city claims that it was the birthplace of the fish taco. They point to the sale of fish tacos in Ensenada’s fish market, the Mercado Negro, as early as 1958. Many Ensenada restaurants advertise that they were the first to create the fish taco.

Perhaps fish tacos were first commercialized there, but their origin likely goes back thousands of years, at least as long as the Indigenous peoples of coastal Mexico have wrapped their ocean catch in a tortilla.

It was Ralph Rubio who popularized fish tacos in the U.S. He tasted them on a spring break trip to Baja California, where, as the story goes, he coaxed a Baja vendor into giving him his recipe for the tacos.

Rubio later established a restaurant in San Diego known as Rubios — Home of the Fish Taco, which later became the Rubio’s Coastal Grill chain.

It’s interesting to note that tacos are typically a morning treat or a nighttime snack in their country of origin. They’re less available between noon and 6 p.m. in Mexico, likely because the main meal there is eaten in the afternoon.

Aren’t we lucky that we can eat tacos here all day long?

Today’s recipe is for mushroom tacos, an option that’s gaining in popularity. Rest assured that these tacos aren’t just for vegetarians, especially if you’re a fungi fan.

While there are many variations on mushroom tacos, the portobellos in this recipe provide a meaty texture and a wonderful burst of umami flavor.

Marinated mushroom tacos with pineapple salsa and lime guacamole

For tacos:

6 portobello mushroom caps, halved
¼ cup extra-virgin olive oil
½ cup orange juice
4 garlic cloves, crushed
2 teaspoons chili powder
1 teaspoon smoked paprika
Juice of two limes
½ cup fresh cilantro leaves, roughly chopped
Salt to taste
Warmed corn tortillas

For pineapple salsa:

½ small pineapple, diced
1 small jalapeño with seeds and pith removed, chopped
Juice of one lime
¼ cup fresh cilantro leaves, chopped
Salt to taste

For guacamole:

2 avocados, peeled, seeded, and mashed
Juice and zest of one lime
Salt to taste

Procedure:

Marinate mushrooms with olive oil, orange juice, garlic, chili powder, paprika, lime juice, cilantro and a pinch of salt to taste. A zipper-sealed bag works well for this. Marinate 10 minutes or as long as overnight in the fridge.

In a bowl, stir together the mashed avocado, lime juice and zest, and salt to taste.

Mix all salsa ingredients together in a separate bowl.

Preheat a grill or grill pan to high. Remove the mushrooms from the marinade and sear for five minutes on each side, or until slightly charred on both sides. Remove from heat and slice into strips.

Spread the guacamole on the warmed tortillas and top with the grilled mushrooms and pineapple salsa.

Enjoy!

Recipe adapted by Esther Oertel.

Esther Oertel is a writer and passionate home cook from a family of chefs. She grew up in a restaurant, where she began creating recipes from a young age. She’s taught culinary classes in a variety of venues in Lake County and previously wrote “The Veggie Girl” column for Lake County News. Most recently she’s taught culinary classes at Sur La Table in Santa Rosa. She lives in Middletown, California.