bug-a-boo vs bugbear

bug-a-boo

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

  • A mythical, nocturnal creature; a hobgoblin. 

bugbear

noun
  • A source of dread; resentment; or irritation. 

  • An ongoing problem; a recurring obstacle or adversity. 

verb
  • To alarm with idle phantoms. 

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