An apparent attempt to drill through the defenses of your peers or associates during haggling or an argument.
It originates from Mistel warheads used by Germans in WWII.
The definitive Mistel warhead was a shaped charge around a core of copper or aluminium. When detonated, the explosion would create a penetrator made of the core of the above mentioned copper or aluminium. The metal would then behave like a liquid (and not, as often falsely reported, liquefy), capable of penetrating up to 7 metres (24 feet) of steel armour. It was anticipated that this would be able to "drill" straight through an enemy warship.
The Mistel was never proven to be affective.
I growled in my thickest Misteldrossian accent.