In some rural areas of Mississippi there are places where "flush toilets" aren't available. The people in those areas have to use out-houses or as they're known in these areas "Mud Holes". They are usually a pieced together shack made of whatever odds and ends can be found in the front yard or that scrap pile at the end of the gravel road. once constructed a hole is dug to catch the leavings, thus creating the mud.
"oh man I really gotta go! Do you have a bathroom?"
to which is answered "Nope, just got that mud hole over yonder"
We were on a road trip down South when we got lost. Dave had to go really bad and ended up having to use a Mississippi Mud Hole behind some guy's house.