bog bilberry vs crackleberry

bog bilberry

noun
  • A shrub native of the cool temperate areas of northern hemisphere, Vaccinium uliginosum, and the berry of that shrub. 

crackleberry

noun
  • The high-bush huckleberry, Gaylussacia baccata, native to eastern North America, or the fruit of this shrub 

  • An imaginary shrub, or the fruit of this shrub 

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