Nightmare

Nightmare (pronounced nahyt-mair)

(1) A terrifying dream in which the dreamer experiences feelings of helplessness, extreme anxiety, sorrow etc.

(2) A condition, thought, or experience suggestive of a nightmare.

(3) A monster or evil spirit once believed to oppress persons during sleep.

1250–1300: From the Middle English nightmare, from the Old English nihtmare, the construct being night +‎ mare (evil spirit believed to afflict a sleeping person).  It was cognate with the Scots nichtmare and nichtmeer, the Dutch nachtmerrie, the Middle Low German nachtmār and the German Nachtmahr.  Another Old English word for it was niht-genga.

Night was from the Middle English nighte, night, nyght, niȝt & naht (night), from the Old English niht, neht, nyht, neaht & næht (night), from the Proto-Germanic nahts (night), from the primitive Indo-European nókwts (night).  It was cognate with the Scots nicht & neicht (night), the West Frisian nacht (night), the Dutch nacht (night), the Low German & German Nacht (night), the Danish nat (night), the Swedish & Norwegian natt (night), the Faroese nátt (night), the Icelandic nótt (night), the Latin nox (night), the Greek νύχτα (nýchta) (night), the Russian ночь (nočʹ) (night) and the Sanskrit नक्ति (nákti) (night).

Mare had a second etymological track from the sense of the female horse (mare from the Old English mīere).  The sense of “nightmare, monster” is from the Old English mare from the Proto-Germanic marǭ (nightmare, incubus) and can be compared with the Dutch dialectical mare, the German dialectical Mahr from the Old Norse mara which produced also the Danish mare and the Swedish mara (incubus, nightmare).  The ultimate root was the primitive Indo-European mor (feminine evil spirit).  The English and European forms were akin to the Old Irish Morrígan (phantom queen), the Albanian merë (horror), the Polish zmora (nightmare), the Czech mura (nightmare, moth) and the Greek Μόρα (Móra); doublet of mara.

The original meaning (incubus, an evil female spirit (later often called a goblin) afflicting men (or horses) in their sleep with a feeling of suffocation) dates from the thirteenth century, with the meaning shift from the incubus to the suffocating sensation it causes emerging in the mid sixteenth century.  The sense of "any bad dream" is recorded by 1829; that of "very distressing experience" is from 1831.  Nightmare and nightmarishness are nouns, nightmarish is an adjective and nightmarishly an adverb; the noun plural is nightmares.

Bad dreams

Nightmares are regarded by mental health clinicians essentially as part of the human condition.  In this they differ from night terror (sometimes called sleep terror), a disorder inducing panic or feelings of morbid dread, typically during the early stages of non-rapid eye movement (NREM) sleep and usually brief in duration, lasting no more than 1-10 minutes.  Sleep terrors appear most often to begin in childhood, decreasing (usually) with age but their frequency and severity can be affected, inter alia, by sleep deprivation, medications, stress, fever and intrinsic sleep disorders.  Evidence does seem to suggest a predisposition to night terrors may be congenital and there may be an increase in prevalence among those with first-degree relatives with a similar history but the link to inheritance is dismissed by some academics as "speculative".

The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM–5, 2013) revised the diagnostic criteria for sleep terror disorder, requiring:

(1) Recurrent periods where the individual abruptly but not completely wakes from sleep, usually occurring during the first third major period of sleep.

(2) The individual experiences intense fear with a panicky scream at the beginning and symptoms of autonomic arousal, such as increased heart rate, heavy breathing, and increased perspiration. The individual cannot be soothed or comforted during the episode.

(3) The individual is unable or almost unable to remember images of the dream (only a single visual scene for example).

(4) The episode is completely forgotten.

(5) The occurrence of the sleep terror episode causes clinically significant distress or impairment in the individual's functioning.

(6) The disturbance is not due to the effects of a substance, general medical condition or medication.

(7) Coexisting mental or medical disorders do not explain the episodes of sleep terrors.

The Nightmare (1781), oil on canvas by Henry Fuseli (1741–1825).

Waking from a nightmare, Lindsay Lohan in Scary Movie 5 (2013)