In 2267, Sylvia and Korob tapped into the Human subconscious and created an illusory world based mostly on Human nightmares and images of Halloween, thinking at the time that this was how Humans existed. Korob later could not understand why Human visitors to this environment acted as if it were so strange, failing himself to understand references to Halloween and the ritual of "trick or treat."
A phrase Korob did pick up on, however, was "mumbo-jumbo," laughing in amusement at Captain James T. Kirk's reference to it and further proclaiming "I assure you it was not that" with regards to the illusion world around him. (TOS: "Catspaw")
Later that year, when Montgomery Scott was on trial for murder on Argelius II, Scott expressed dismay at the Argelian Empathic Contact ceremony, asking if "his neck was going to depend on some spooky mumbo-jumbo." (TOS: "Wolf in the Fold")