bugaboo

Bugaboo has been used since the early 1700s to refer to an imagined problem or bugbear (although oddly, in 19th century English, it was also used as a nickname for a bailiff). The word itself has two possible origins, both of which are equally ghoulish: It might come from an old Celtic word (most likely bucca-boo, an old Cornish word for a devil or spectre), or it might come from “Bugibu,” the name of a monstrous demon that appeared in a Medieval French poem, Aliscans, written in the mid-1100s.