interbreed vs intercross

interbreed

verb
  • To breed or reproduce within a heterogenous community, the products of which produce hybrids. 

  • To breed or reproduce within an isolated community. 

intercross

verb
  • To breed two strains having a common ancestry with one another 

  • To cross back over one another 

noun
  • The act or product of intercrossing 

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