The term ephialtes nocturnus comes from the Greek noun ephialtes (leaper, 'the one who jumps upon') and the Latin adjective nocturnus (nightly). It is used in the older literature as a synonym for " nightmare. The term ephialtes noctur-nus is usedinopposition to "ephialtes vigilantium (i.e. " daymare).
References
Good, J.M. (1823). The study of medicine. In four volumes. Boston, MA: Wells and Lilly.
Dictionary of Hallucinations. J.D. Blom. 2010.