Mexico comes from the Spanish “México,” a name derived from the Classical Nahuatl “Mēxihco,” a kingdom that encompassed most of the western shores of Lake Tetzcohco, Lake Xāltocān, and Lake Tzompanco, ruled from the famous island on which the twin cities of Tenōchtitlan and Tlatelōlco were established.
The “x” of Mēxihco is pronounced like English “sh.” The line above the “e” indicates that it is long (held twice the duration of a normal “e,” like the difference between the vowels in “bed” and “bet”). The “h” stands for a glottal stop (a sort of hitch in the back of the throat). “Mēxihco” breaks down into the root “mēxih” and the suffix of place “-co.” The meaning of “mēxih” is debated, though if we add the absolute suffix to the root (in order to make it a normal noun), we get something like mēxihtli or mēxitl. But what does that mean? There’s the rub.
The people we call Aztecs were principally governed by the inhabitants of Mēxihco Tenōchtitlan (the full name of Mexico City in Nahuatl). They called themselves Mēxihcah or Tenōchcah and claimed that before settling in the Valley of Mexico they had been known as the Mexihtin. This ethnonym, they affirmed, was derived either from the name of the leader who guided them out of the mythical land of Aztlan, Mecihtli (“agave hare”), or from Mēxihtli, a title of the tribal god Huitzilopochtli.
On this view, then, Mēxihco means “land of the Mexihtin” or “land of Mēxihtli.” The problem with “land of the Mexihtin,” however, is the vowel: the long “ē” of Mēxihco would not normally arise from the short e of Mexihtin (this also makes it unlikely that Mexihtin derives from Mēxihtli). From a linguistic standpoint, the Aztecs were engaging in a a bit of “folk etymology,” an after-the-fact explanation tacked on by people who do not truly know a word’s origin.
Other etymologies have been proposed, of course. The lake in the midst of which the Mexihtin found an island to settle upon was called by the nearby inhabitants “Mētztli īāpan” or “Moon Lake.” It has been posited that this island in the center of Moon Lake would have been referred to as “Mētztli īāpan īxīc” or “the bellybutton of Moon Lake,” perhaps shortened to “Mētztli īxīc” / “Mētzxīctli” (bellybutton of the moon). This hypothetical word is formed along the same lines as “Tlālxīctli” (bellybutton of the earth), which was the name of Tenōchtitlan’s temple to the god of the underworld, Mictlāntēuctli.
When you add the locative suffix -co you get “Mētzxīcco” (place of the moon’s bellybutton).
Now, there are three processes that possibly support the theory that this word could have become “Mēxihco.” First, regressive assimilation. Following the consonant “tz” with “x” in Nahuatl often leads to the former being assimilated by the latter. In such a case, we would have “Mēxxīcco.”
Then degemination. Sometimes doubled consonants (usually pronounced as a single long one) can be synthesized into just one, giving us “Mēxīcco.”
And, finally, dissimilation. In some modern dialects of Nahuatl, /kk/ can be reduced to /hk/ or /ɦk/ (those first sounds evolved from the glottal stop). If such dissimilation happened in pre-Colombian Nahuatl (and mind you, there is no evidence of it anywhere), then the word conceivably have become “Mēxīhco.”
However, once again there is a derivation issue: “Mēxihco” does not have a long “ī,” which throws a wrench into this already very convoluted theory as to the origin of Mēxihco.
Finally, some believe the name comes from “metl” (agave) plus īxīc and -co, but the resulting compound (“in the center of the agave”) would be Meīxīcco or Mexīcco, with the same derivation issues as described above.
The most likely of all these proposed origins is “land of Mēxihtli,” which has none of the linguistic problems of the other explanations. As Huitzilopochtli was the primary tribal god of the Mēxihcah, their naming themselves and their promised land after him is imminently believable.
However, we may never be certain. So much evidence is now lost to us. The mysticism of the state religion of the Triple Alliance (the “Aztec Empire”), which burned the original histories of the Mēxihcah a century before the Spanish Conquest, had led to many fanciful folk etymologies by the early 16th century, and these have been propagated to the present in the works of colonizers who further erased the past and armchair linguists attempting to discover a mystical meaning for Mexico.