The world’s airports are identified by three-letter codes known as IATA station identifiers. You’ve no doubt seen them on your baggage tags when you were flying somewhere.
Some of them are abbreviations of the cities they are located in like MEX for Aeropuerto Internacional Benito Juárez in Mexico City while others are derived from the airport’s name like JFK for John F. Kennedy Airport in New York City.
Some, however, seem to make no sense, but they are often references to historical names like ORD for O’Hare in Chicago. It’s former name was Orchard Field. And in the case of Canada, it gets complicated with which one has a weather station and which one does not.
It’s all explained on this Wikipedia page.