Why did the spanish decide to name Tenochtitlan Mexico city?

The Spanish did not name Tenochtitlan Mexico City. The city was founded by the Aztecs in 1325 and named Tenochtitlan. When the Spanish conquered the Aztec Empire in 1521, they built a new city on the ruins of Tenochtitlan and named it Mexico City. The name "Mexico" comes from the Nahuatl word "Mēxihco", which means "place of the Mexica". The Mexica were the Aztec people who founded Tenochtitlan.