Tenochtitlan was a Cultural Melting Pot
The Aztec Empire was not too dissimilar from European empires of the same era, and people from across the Aztec domain, of varying ethnicities and cultures, came together to live in Tenochtitlan. The original Aztecs called themselves the Mexica, or alternatively, Tenochca, but there were plenty of other cultures and ethnic groups within the Aztec Empire as well.