In our research at Waverly Plantation, we asked the African American
tenant farmers who had lived there in the 1900-1930 period several
questions regarding their use of privies. We were told that they did not
have privies, but went in the woods.
 
I think this is a result of a belief system involving sorcery, voodoo,
etc., in which one hides any product of the body--like hair, nail
clippings, and feces--so that these cannot be used against oneself.
 
Bill Adams