File is a condiment necessary for Creole or Cajun cuisine, and it is often known as gumbo file because it is the condiment that gives gumbo its particular characteristics. File dates back to the Choctaw Indians of the Gulf Coast, who ground sassafras leaves and added the resulting powder to soups. Later on, the early Cajuns adopted the use of file for their cuisine.
Sassafras is a 20- to 30-foot-tall tree that grows from the Southeastern United States to East Texas. When ground, this condiment smells like eucalyptus. It acts as a thickener, but should only be added after removing the gumbo or other dish from the heat, in order to prevent the file from becoming tough and stringy.