This World War II-era U.S. Navy white hat originated in the 1880s when white canvas hats with a similar structure first appeared. Its original purpose was to protect the head from hot, intense sunlight. Normally, the brim is turned up, but it can be turned down to protect the ears if necessary. Over the years, the cap became as much of a tradition as the sailors' spring and summer white cotton uniforms, autumn and winter blue wool uniforms, and everyday denim.
The white caps are for soldiers below the sergeant level. When worn, the upturned brim takes on the shape of a cup. This feature has earned it the nickname Dixie Cup (because of the small disposable paper cup of the same name).