I am really really sure I don't have something called file powder. Just what part of the grocery store has such a thing?
Chances are you don't, and neither will your grocery store.
If they do it will be in the aisle with the bottled spices, but it is not a popular spice, and therefor not stocked in a lot of stores. It is also optional. (I don't like the taste and never use it.)
Filé powder, pronouned "FEE-lay", is made of ground sassafras leaves, native to the southern U.S. Filé was introduced to Cajun settlers by the Choctaw Indians who helped the settlers survive in the wilderness.
Filé powder should not be added until the very end of cooking; boiling filé will cause the whole pot of gumbo to become stringy and gummy. Even better is to add the filé to each individual bowl of gumbo (about ¼ teaspoon stirred into each bowl), especially if you plan on having leftovers to reheat later.
Most people do not use Okra and Filé together in the same gumbo, because it will make the gumbo thicker than usual. BTW, did you know Okra was introduced in the U.S. by African slaves? In Umbundu (a language spoken in Angola, where many Southern slaves came from) the word for okra is "ochingombo
", which was eventually abridged to "gombo." And the Choctaw word for sassafras is "kombo