In 1897, Nashville candy makers William Morrison and John C. Wharton invented cotton candy. They invented a device that heated sugar in a spinning bowl that had tiny holes in it. It formed cotton candy and they called it Fairy Floss. As the bowl spun around, the caramelized sugar was forced through the tiny holes, making feathery candy that melts in the mouth.
Morrison and Wharton introduced Fairy Floss in the 1904 St. Louis World's Fair. They sold a lot of boxes for 25 cents each, which was a lot back then. The term cotton candy began in the US around the 1920s. The UK use the term candy floss.