A bugbear is a creature or type of hobgoblin comparable to the bogeyman, bogey, bugaboo, and other creatures of folklore, all of which were historically used in some cultures to frighten disobedient children. In medieval England, the Bugbear was depicted as a creepy bear that lurked in the woods to scare children.
In a modern context, the term bugbear serves as a metaphor for something which is annoying or irritating. It may also mean "pet peeve". Bugbear is also another term for scarecrow. - edited from Wikipedia

Oscar of New York