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The Collaborative International Dictionary

Ephialtes \Eph`i*al"tes\, n. [NL., fr. Gr. ?, lit., one who leaps upon.] The nightmare.
--Brande & C.

Douglas Harper's Etymology Dictionary

nightmare or demon that causes nightmares, c.1600, from Greek Ephialtes, name of a demon supposed to cause nightmares; the ancient explanation is that it was from ephallesthai "to leap upon," which suits the sense, but OED finds "considerable" phonological difficulties with this.


n. (context obsolete English) an incubus; a nightmare


Ephialtes (, Ephialtēs) was an ancient Athenian politician and an early leader of the democratic movement there. In the late 460s BC, he oversaw reforms that diminished the power of the Areopagus, a traditional bastion of conservatism, and which are considered by many modern historians to mark the beginning of the "radical democracy" for which Athens would become famous. These powers included the scrutiny and control of office holders, and the judicial functions in state trials. He introduced pay for public officeholders, reduced the property qualifications for holding a public office, and created a new definition of citizenship. Ephialtes, however, would not live to participate in this new form of government for long. In 461 BC, he was assassinated, probably at the instigation of resentful oligarchs, and the political leadership of Athens passed to his deputy, Pericles.

Ephialtes (disambiguation)

Ephialtes was a fifth century BC Athenian statesman

Ephialtes may also refer to:

  • Ephialtes, in Greek mythology, one of the twin Aloadae, possibly the same as the Giant (below)
  • Ephialtes, in Greek mythology, one of the Giants, possibly the same as the Aloadae (above)
  • Ephialtes (illness), name given in the 18th century to an anxiety disorder
  • Ephialtes of Trachis, soldier who betrayed the Spartan army at Thermopylae to the Persians
Ephialtes (illness)

Ephialtes (lit. "jumping on you") is an anxiety disorder identified as such by John Bond in 1753, along with other authors of those times, in his treatise "Incubus". The famous Greek physician Galen in the 2nd century AD had already named nightmares "Ephialtes".

The idea of an incubus as a causative factor in nightmares stemmed from the belief that some spirit or ghostly person crept in during the night and lay upon the sleeper, so as to constrict the chest and breathing—leading to a sense of suffocation, side by side with a terrifying dream of being either crushed or (in the case of a woman) sexually violated by the (male) incubus or ephialtes. Sleepers thus set upon feel they are about to die—but as Bond (who was himself prone to nightmares) stated: "As soon as they shake off that vast oppression, they are affected with a strong palpitation, great anxiety, languour, and uneasiness – which symptoms gradually abate, and are succeeded by the pleasing reflection of having escaped such imminent danger"(p. 3).

Usage examples of "ephialtes".

When Ephialtes was assassinated for his pains, the leadership passed to the young Pericles, whose first move was to make peace with Persia.

But a traitor by the name of Ephialtes who knew the little byways of Malis guided a regiment of Persians through the hills and made it possible for them to attack Leonidas in the rear.