Usage 1: Modern English speakers have, by and large, given up the meaning of a female goblin called a nightmare in favor of a bad dream of any sort. But Shakespeare clearly used the word in the original meaning in King Lear, III, iv, 126: "He met the night-mare and her nine-fold; Bid her alight, And her troth plight, And, aroint thee, witch, aroint thee" (i.e. Away with thee!) The adjective (like the demon) is "nightmarish" and the adverb is "nightmarishly."

Suggested usage: Using the word in its original meaning implies a belief in goblins and spirits: "He awoke in the morning looking (and feeling) like he had been accosted by a nightmare." So long as we avoid using it to refer to our wives and girl friends, no harm will be done. Otherwise, the common sense is always useful, "The traffic in downtown Lewisburg was a nightmare today."

Etymology: Middle English, a female demon that attacks sleeping people; based on night "night" + mare "goblin." "Night" is from a verbal root *negw- "to be dark" which turns up in German Nacht, Latin nox, noctis, Greek nux, and Russian noch'. It also underlies Latin niger "black," which devolved into Italian negro "black." Old English mare means "goblin, incubus" and is related to Latin mori "die," found in "mortal," "morbid," and to English "murder." (Thanks to Julie Langford-Johnson of the University of Indiana for yet another seasonal word of the day.)