For the Pocket TNG, please see Boogeymen.
The boogeyman was a mythic creature or monster in folklore that was sometimes used by adults, particularly parents or other authority figures, to instill fear in children so that they behaved appropriately. The term was also used to personify fear and evil.
In 2259, Captain Marie Batel noted to Captain Christopher Pike that she kept hearing rumors that the Romulans were developing new weapons. Pike responded by referring to the Romulans as the boogeymen, because no one had ever seen one or knew what they looked like, yet the Romulans were blamed for a lot of things. (SNW: "A Quality of Mercy")