bug-a-boo vs hobgoblin

bug-a-boo

noun
  • Any imagined fear or threat, or a fear presumed larger than it really is. 

  • A mythical, nocturnal creature; a hobgoblin. 

hobgoblin

noun
  • A source of dread, fear or apprehension; a bugbear. 

  • A small, ugly goblin that makes trouble for humans. 

How often have the words bug-a-boo and hobgoblin occurred in a corpus of books? (source: Google Ngram Viewer )