Santiago was a very popular name for the conquistadors to use as they rechristen the new lands of the American continent. If you check the entry for Santiago in Wikipedia, you will there are over 60 cities and towns throught the world that carry that name and that is a very short list since you could probably find about 60 towns with the Santiago name, just in Guatemala. But why was Santiago such a popular name for the Spanish and Portuguese conquistadors?
The English-language speaking community refuses to recognize the official name of La Antigua Guatemala because it is too long or lack of knowledge or poor Spanish-language skills; who knows really?. They just want to call it Antigua. But Antigua is a Caribbean Island. Yet, they refuse to call it La Antigua Guatemala, which, by the way, simply means the former Guatemala City.
To add to this confusion, many Guatemalans just call it Antigua too, although more often they say La Antigua. This error is even published by newspapers and magazine. Worst yet, the road signs just say Antigua Guatemala. Even Wikipedia just have it listed as Antigua Guatemala, which by the way means Old Guatemala.