It turns out that “nightmare” and “cauchmar” (French for nightmare) share the same root, mare, which refers to a demon or ghost that presses on the chest during sleep and causes a feeling of suffocation.
This specifically causes a phenomenon that is now medically referred to as sleep paralysis. It is believed that 7.5% of people have experienced it at least once in their life, and among psychiatric hospital patients, the percentage is five times higher.
Hi, I'm Rauf Aliev. 