E. Cobham Brewer 1810–1897. Dictionary of Phrase and Fable. 1898.
In’cubus.
A nightmare, anything that weighs heavily on the mind. At one time supposed to consort with women in their sleep. (Latin, in cubo, to lie on.)
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“Merlin was the son of no mortal father, but of an Incubus; one of a class of beings not absolutely wicked, but far from good, who inhabit the regions of the air.”—Bulfinch: Age of Chivalry, part i. chap. iii. p. 50.
