(n.) a disturbed night’s sleep, a sleep broken by nightmares
File this one away for later use: oneirodynia is a disturbed night’s sleep caused by nightmares.
That’s a term from psychology that first appeared in English in an 1800 dictionary of nosology (the science of diseases), defined as “inflamed or disturbed imagination during sleep.”
Before then, there’s a slightly earlier record of this term being used in French, and Latin before that, but at its etymological root are the Greek words oneiros, meaning “dream,” and odyne, meaning “pain,” or literally, “great anguish.”
Neither of those are the most familiar of word roots in English, of course, but that’s not to say that they aren’t fruitful. The suffix –dynia, for instance, is a lesson common version of –algia, used to form the names of specific aches and pains like cardiodynia (heart pain), neurodynia (nerve pain), cephalodynia (a headache), and allodynia (a pain caused by a stimulus that should not or does not normally cause pain, like laughing or tickling).
Likewise, as well as oneirodynia the dictionary has entires for words like euneirophrenia (the pleasant state of mind that follows waking up after a nice dream) and its opposite malneirophrenia (the feeling that follows a nightmare); oneirocriticism (the interpretation of dreams) and oneirocritic (someone who does precisely that); oneirology (the study of dreams); nudoneiria (dreaming that you’re naked); and oneirataxia (the inability to differentiate between dreams and reality).