A Nightmare is the terrible dream like inability to run from a dangerous situation, losing your or gadgets or a bad time in a person’s life. But it has nothing to do with Mare. Although Sigmund Freud considered as the father of modern psychology described the dreams as the awakening of the subconscious mind and fulfillment of the unfulfilled desires.
Coming to the origin of the word, it consists of two words fused together. Night and Mare. Mare is derived from middle English word Mare which meant a “female evil spirit thought to lie upon and suffocate sleepers’. This had developed from mære in Old English – so it’s clear concerns about anything that interrupts a good night’s sleep have been around for a long time. In those olden times our understanding of the working of our brain was not good and mythology provided the explanations. Mare has been prefixed to emphasise the sleep time occurence.
Other cultures also have many words with many describing evil spirits, demons or goblin-like creatures which would ride on people’s chests while they slept, bringing on bad dreams.