bugbear vs bugaboo

bugbear and bugaboo both are nouns.

Word	Noun	Adjective	Verb	Adverb
bugbear	Yes	No	No	No
bugaboo	Yes	No	No	No

As nouns, bugbear and bugaboo are synonyms defined as:

Other synonyms of bugbear include bogeyman, booger, boogeyman.

bugbear (noun)	bugaboo (noun)
an object of dread or apprehension	a source of concern
an imaginary monster used to frighten children	an imaginary monster used to frighten children