filé ('fee lay) powder, or gumbo filé, is powdered dried sassafras leaves. It's traditionally used in Creole and Cajun dishes, to help thicken sauces and add flavor. I've seen it described as an earthy or woodsy flavor...I'm bad at flavor descriptions, but that seems about right. It should be added at the very end of cooking because overcooking makes it stringy.
tasso is a special type of flavorful cured and smoked pork used in Cajun cuisine; it isn't eaten on its own but is instead used as flavoring.
gumbo is a stew of seafood or chicken, sausage, onions, bell peppers, celery, okra, filé powder, and other ingredients, served over rice. There are many variations on the basic recipe; the Cajun version often uses tasso. Okra and filé powder both help to thicken the stew. Gumbo is a multi-cultural invention: okra from Africa, filé from the Native Americans, cooking methods from the French, and contributions from many others as well.
The most reliable word origin I've found says filé comes from the French verb filer, to twist or spin. Another source suggest fil, thread or string.
I couldn't find a word origin for tasso...tasse is French for cup. Tasso in Italian means rate or measure.
Gumbo is a variation of one or more West African words for okra.
Sassafras was first used by the Choctaw Indians who inhabited the Louisiana bayou country. Sassafras root used to be used for flavoring root beer, but this has since stopped due to the presence of potentially-carcinogenic safrole (the leaves are safe). Safrole can be found in small amounts in many food ingredients, including cinnamon and nutmeg, and consumption should be limited during pregnancy. Safrole is currently known for its role in the recreational drug MDMA (Ecstasy).
This is my first food-themed post. Keep me honest: let me know if I stray too far from word trivia and too close to food trivia.