Bumfuck vs backwoods

Bumfuck

name
  • An imaginary place in the middle of nowhere. 

backwoods

noun
  • Partly or wholly uncleared forest, especially in North America. 

  • A remote or sparsely inhabited region, especially in North America; away from big towns and from the influence of modern life. 

adj
  • Rough, uncouth, coarse, or crude in social matters. 

  • Pertaining to the backwoods. 

How often have the words Bumfuck and backwoods occurred in a corpus of books? (source: Google Ngram Viewer )