The State of Mexico is often abbreviated to "Edomex" from Estado de México in Spanish, to distinguish it from the name of the whole country. It is located in South-Central Mexico. It is bordered by the states of Querétaro and Hidalgo to the north, Morelos and Guerrero to the south, Michoacán to the west, Tlaxcala and Puebla to the east, and surrounds on three sides Mexico City (the former Federal District).
The state's origins are in the territory of the Aztec Empire, which remained a political division of New Spain during the Spanish colonial period. After gaining independence, Mexico City was chosen as the capital of the new nation; its territory was separated out of the state. Years later, parts of the state were broken off to form the states of Hidalgo, Guerrero and Morelos. These territorial separations have left the state with the size and shape it has today, with the Toluca Valley to the west of Mexico City and a panhandle that extends around the north and east of this entity.
The state name is simply México according to the 1917 Constitution of the United Mexican States, but to distinguish it from both the city and the country it is most often called Estado de México. The demonym used to refer to people and things from the state is mexiquense, distinct from mexicano ("Mexican"), which describes the people or things from the country as a whole.
Mēxihco was originally the Nahuatl name for the Valley of Mexico where the cities of the Mexica (the proper name for the Aztec Triple Alliance) were located. As such, the district that became Mexico City was properly known as Mexico-Tenochtitlan in the years shortly before and after Spanish conquest. After the Spanish Conquest, the term México came to be used for Tenochtitlan/Mexico City and all the pre-conquest lands it controlled, including several other aforementioned Mexican states originally incorporated in the boundaries of the Mexico state.
There are two possible origins for the name “Mexico.” The first is that it derives from metztli (moon) and xictla (navel) to mean from the navel of the moon. This comes from the old Aztec idea that the craters on the moon form a rabbit figure with one crater imitating a navel. The other possible origin is that it is derived from “Mextictli” an alternate name for the god Huitzilopochtli.
Anáhuac was the proper term for all territories dominated by the Aztec Empire, from Cem Anáhuac, "the entire earth" or "surrounded by waters" e.g. the waters of Lake Texcoco which were considered to be the center of the Aztec world, and as such was proposed as an early name for the entire nation of Mexico prior to independence, to distinguish it from the (preexisting) administrative division of New Spain that became the State of Mexico.