No later than at the beginning of the 20th century, the small town of Pecka, located in the foothills of the Giant (Krkonose) Mountains, today part of the district of Jicin, Northeast Bohemia, then in a region on the Czech-German language border, saw the birth of a local warning creature, a children’s bugaboo with the unusual name of Kumraus. Its name derives from the imperative form of the German verb “(he)rauskommen”, i.e. to go out. The phrase „Komm raus!“ (Come out! Creep out! Come!), at that time used by the local German families to call a bugaboo on naughty children, was passed in the same context into the Czech language milieu, where an otherwise ordinary German imperative form became the awful-sounding proper name of a newly conjured supernatural creature, a bugaboo called Komraus or Kumraus, which came to be used to frighten Czech children. What was typical for this bugaboo was the complete absence of any specific appearance. Adults never told their children how it looked like; Kumraus was only an abstract term, a name that itself sounded frightening and stirred the children’s imagination. The bugaboo that could take children and carry them away occurred simultaneously in two roles: either as a supernatural creature closely linked to the dusk and warning children from staying outside when they were not supposed to, or as a bugaboo that came whenever the parents needed and at any time of day. There is evidence of Kumraus being sighted in the dark cellars of family houses, so typical for children’s bugaboos. The small town of Pecka is most likely the place where this warning creature originated and is also the main place where it occurs. Although account must be taken of the fact that the folklore tradition did to a certain extent overlap into the surrounding villages, as far as we are aware the creature of Kumraus appears to be a specific phenomenon for Pecka. This was a vital folklore tradition throughout virtually the whole of the 20th century. At the time of the author’s field work in 2017–2018, however, the awareness of Pecka’s bugaboo remained only a part of the latent repertoire of the last of the local old-timers (a total of 8 stories were told and recorded). From the linguistic point of view, the creature known as Kumraus is not only an interesting case of the remarkable development of a demonic creature, but also evidence of the former Czech-German language border as well as the local German dialect.