back country vs boondocks

back country and boondocks both are nouns.

Word	Noun	Adjective	Verb	Adverb
back country	Yes	No	No	No
boondocks	Yes	No	No	No

As nouns, back country and boondocks are synonyms defined as:

Other synonyms of back country include backwoods, hinterland.

back country (noun)	boondocks (noun)
a remote and undeveloped area	a remote and undeveloped area