The first property to use "JW Marriott" as part of its name was the JW Marriott Washington, DC, which was built in 1984.
Although it marked the beginning of the JW Marriott brand, it was not originally promoted as a separate brand in today's sense. It was a particularly well-located and well-appointed Marriott hotel, deserving an identify that would set it apart from the rest of the Marriott chain. The name of the hotel was a tribute to J. Willard Marriott Sr. (1900-1985), who was still alive when the hotel opened.
Marriott had a separate, second brand: Courtyard by Marriott. The first test locations opened in 1983. Then, in 1984, Marriott announced that the test was successful and the brand would be rolled out.
In 1984, Marriott had also owned restaurant chains, airline catering, tollroad service plaza restaurant concessions, and theme parks (although, in 1984, Marriott announced it would be exiting from the theme park business).
Marriott -- and the entire hotel industry -- was very different back in 1984.