Picture by Andrew L. Paciorek
The Boogeyman, more traditionally spelled “Bogeyman,” does not seem to be a reference to any specific monster, but rather to any scary creature that is either the product of a child’s imagination or used by parents to scare children. These include the traditional monster that lives in the closet or under the bed, essentially a manifestation of fear of the dark and the unknown.
More specific bogeyman-type beings include the scissor man that will cut off a kid’s fingers if they suck on them, and variations on the theme of a guy who takes bad children away in a sack.
This page lists some of the more interesting regional variations. It’s been suggested that the word “bogeyman” might come from the Bugis, who were Indonesian pirates, but this is considered unlikely due to the fact that the word was used in Europe before there was much contact between the Europeans and Indonesia. The term is almost certainly related to the boggarts, who were mischievous house fairies responsible for stealing household items, making milk go sour, and placing clammy hands on the foreheads of sleepers. It was said that they could be kept out of a house by placing a horseshoe above the door, a pretty standard safeguard against evil fairies and the like. Boggarts are part of English folklore (the Scots call them bogles), so the name for this one sort of malevolent house monster probably eventually came to be applied to other creatures of the same general sort. I don’t know if there’s any direct connection between boggarts/bogeymen and “bogey” or “booger” as a slang term for mucus, but they might well have common roots. I understand that the word “bug” also came from the same Middle English word, so it probably came to mean anything obnoxious or gross.
In Terry Pratchett’s Discworld, bogeymen are a species of their own, albeit a fairly rare one. I believe the first bogeyman we meet in the series is Schleppel in Reaper Man, who’s agoraphobic and hence has the hiding part down, but isn’t so keen on the jumping out at people. In Hogfather, the original bogeyman, a manifestation of primal terror, is revealed to also have been the first tooth fairy. Since children believe that bogeymen stop existing when they hide under blankets, putting a blanket over a bogeyman’s own head will cause him to doubt his own existence.
Another memorable appearance by a bogeyman in twentieth-century media is Oogie Boogie from The Nightmare Before Christmas, who is basically a giant potato sack stuffed with bugs.