Nantucket is called "ACK" because ACK is the official three-letter Federal Aviation Administration (FAA) airport code for Nantucket Memorial Airport. The code "ACK" is derived from letters in the word "Nantucket." Over time, this code has become a shorthand or nickname that locals and visitors often use to refer to Nantucket, not just the airport itself. The use of "ACK" as a nickname is popular in branding and local culture, symbolizing the connection people have with the island, especially among travelers and tourists.
