Unlike those names for the ravers that originate from the Indian subcontinent, these three names, all from Middle Eastern sources, make a lot more sense:-
Jehannum is directly related to the Arabic "jahannam", itself related to the Hebrew word "gehenna" and describes the Islamic conception of Hell. Similar to other religions, jahannam is a fiery pit into which the damned will be cast to suffer for all eternity.
Herem could have several etymological roots, but the most likely is again the Arabic word "haram", originating from the Hebraic "herem". In Islam, "haram" is a term reserved to describe the most morally repugnant and loathsome of sins, a transgression so heinous that it warrants excommunication, expulsion or exile.
The roots of the word Sheol are simpler; it's taken straight from the Hebrew and refers to the underworld or abode of the dead. This is a place of unrelenting sterility and utter darkness, utterly cut off from the grace and presence of God.
Taken at face value, this set of names seems to be entirely more appropriate for those distillations of pure evil and malevolence that are the ravers.
Roles in the ChroniclesEdit
Please refer to the more general wiki article on the ravers that can be found here.