The meaning of this word has its roots in quantum mechanics. In essence, when a person goes to lay a grogan in the shitter, quantum theory states that there is a finite (although very small) probability that the shitter will actually lay a grogan into the person. This occurence is very rare and it is said the victims of the Nagorg reach a deeply spiritual (and highly painful) state.
The word Nagorg applies to a grogaN in reserve, hence its name.
After receiving his third nagorg in as many weeks from the local dunny at the pub, Unwin promptly left town.