What happens if I short the starter leads?

I was playing around with my starter, and of course the negative terminal fell BACK onto the battery, and I think I shorted the leads, because now nothing gets power, and the battery's voltage is fluctuating between 11v and 7v. I was making small talk at a buddy's shop and someone said it sounded like a bad BCM (Body Control Module). I've never heard of this, and I'm definitely not close enough to this shop for them to stop trying to get me to buy things I don't need, so is the BCM a legitimate thing? Any other ideas?
It's a 1998 XJ with a manual trans.

The ECM regulates voltage off the alternator so if you see this with the engine running but don't see it with engine off then yeah it's possible. If you see it all the time I'd assume battery is fubar'd

It's all the time. I hope it's just the battery. nothing gets power, much less the jeep starting. Let's pretend it isn't the battery. What else could it be? I'm trying to cover all the bases since with my luck it won't be that easy.

Did you check all the fuses in the Power distribution center? Relays?

Start by checking all fuses and relays. I would also disconnect the battery (both leads) for about half an hour, touch the leads together for 15 seconds, hook it back up and see if the jeep will start. This will reset the computer, in case something inside it got corrupted, or the sudden drop in voltage confused it.. I would also check the "megafuse" if yours has it, maybe it is blown. Look for burned/melted fusable links at the PDC too...

what is voltage reading on the battery when you monitor it directly

if it's not the battery another possibility would be the fusible link maybe

Jeep Cherokees don't have a BCM. They do have an EC/PCM though (engine control unit/powertrain control module.)

Your battery is already too low to function. You will have to charge it up (hopefully overnight). And check for blown fuses and fusible links.

ok, even if the battery was about gone (7v-11v) you should be able to get radio, lights, chimes - the low draw items. If you are getting those, you have either a-blown the main engine/ecu fuses or b- cooked an ECU. If you hook up a charger, you will "eliminate" the battery from the equation, and mike sure all fuses are good. at this point, do the gauges read anything? At very least does it show battery voltage? if not, you most likely have a dead ECU as all your gauges, starter and fuel pump are controlled by it.

Defiance665 - you can only unhook the battery and short the terminals on pre-95 vehicles that are OBD 1. OBD II (all vehicles 95 and newer) can only have the ECU/ECM/PCM (whatever you want to call it) reset with a scan tool.