Down here in Oz Thunderbox refers to a toilet (although an old fashioned saying). I think it's derived from old days when the toilet was out the back before sewerage/septic tanks were installed. The wooden box/seat was above the pan (the Thunderbox) which was collected from the "dunny guy" that used a laneway between the rear of houses to empty the "dunny pan". Anyone who has used a thunderbox during an Ozzie summer knows why it's called a thunderbox.

Anything else?