In an early version of the Psalms, in the place of the words "from the pestilence that walketh in darkness," in the 91st Psalm, we have "from the Bug that walketh in darkness." "A Bug," says Bayle, in his English Dictionary of 1755, is "an imaginary monster to frighten children with."
Each trembling leaf and whistling wind they hear,
As ghastly bug their hair on end doth rear,
wrote Spenser in the Faerie Queene. And Shakespeare uses the word several times. In The Taming of the Shrew: "Tush! tush! fear (frighten) boys with bugs." In The Winter's Tale: "The bug, which you would frighten me with, I seek." "We have a horror for uncouth monsters," wrote L'Estrange; "but upon experience, all these bugs grow familiar and easy to us." We use the word still in the form of Bogie and Bugbear and Bogart.
By its root we know that the word belongs to the same series of ideas as the Irish Phooka, the English Puck, the German SpUk, and our modern work Spook But whence came this form of the word? Sir Walter Scott, in Harold the Dauntless, makes Jutta, the outlaw's wife, by the Tyne, invoke Zernebock, by which is meant Tchemebog--the Black God, a Sclavonic deity.