"Dieseling" is a bit of a misnomer, but not too far off the mark. The engine is running without an electronic spark, like a diesel.
What's happening is things are so hot that as the intake (carburetor -- this rarely if ever happens with fuel injection since it's computer-controlled and fuel stops flowing when you turn off the key) charge continues flowing into the cylinders, it lights up immediately. WAY before it would if it were happening when the spark plug fires. And it's more of an explosion than a controlled burn, causing the pistons to rattle and wobble, resulting in the noise you're hearing. It can break pistons. Or start an under-hood fire as the fuel-air mixture ignites while an intake valve is still open, sending fire up the intake port and through the carburetor, which has a reservoir containing about half a cup of gasoline. BTW, it's exactly this that's a true "backfire". Backfiring doesn't happen through the exhaust.
The correct term is "pre-detonation" because the fuel-air charge is detonating before it's supposed to. And in a carbureted engine, fuel-air is delivered as long as the engine continues to turn and the pistons make the required suction on their way down the cylinders.
Pinging or knock is a "lite" version of pre-detonation. For any of a number of reasons (octane too low, compression too high, ignition timing too advanced, cylinder temperature too high) the fuel burn is happening too soon and causes the noise.
I could imagine that if pre-detonation were extreme enough, it'd be possible for the engine to start running backwards. It has a lot in common with a diesel at that point. But the engine wouldn't necessarily start running backwards and it'd actually be pretty unlikely since it'd have to do so against the rather massive momentum of the flywheel and other heavy moving parts like the crankshaft.
The pre-detonation would have to happen with sufficient force to STOP the flywheel and start it back up the other direction.
