A yiddish word meaning explode, or burst.
One would plotz with anticipation. One would plotz with laughter. One would plotz with surprise, or delight, or intensity.
It is possible that the word has come to mean faint. A plausible reason would be that in any sentence where plotz is used, the context is ambiguous enough to allow for interchangeable translation of either 'faint' or 'burst'.