(CNN) -- It's the one fact about Mexico that you probably didn't know. The country's name is not really Mexico, at least not officially. After gaining independence from Spain in 1821, Mexico officially became the "Mexican United States."

The American independence movement had inspired Mexican leaders of that era and since Mexico, in fact, also was a territory composed of states, the name stuck and became official in 1824.

But the reality is the official name is used only by Mexican officials who deal with diplomatic protocol and official documents pertaining to international relations. For the rest of Mexicans -- and the world -- the country is simply known as Mexico.

That's why outgoing Mexican President Felipe Calderon on Thursday sent to the Mexican Congress a piece of legislation to change the country's name officially to simply Mexico.

Calderon, a conservative president better known for his war on drug cartels and organized crime, is literally in his last days in office. Enrique Pena Nieto, who was elected in July, takes office on December 1.

It's still too early to know if the new Mexican Congress will quickly act on Calderon's bill or tackle other more pressing matters like security and the economy.

In announcing his decision to propose officially changing his country's name, Calderon said Thursday the name Mexican United States was originally taken because back in 1824 the United States of America was an example of democracy and liberty for the new independent nations in the Americas.

"It's time that we Mexicans retake the beauty and simplicity of our motherland's name: Mexico. (It's) a name that we use when chanting or singing, a name that identifies us throughout the world and that makes us proud," Calderon said.

"Mexico" is a word first used by the Aztecs in their original nahuatl language. The indigenous tribe founded a city called Tenochtitlan in the valley now occupied by the modern Mexico City. That original city was conquered by the Spanish in 1521.

Mexico gained its independence from Spain in 1821. In Spanish, Mexicans pronounce the "x" in Mexico as a hard "h."