cross-breed vs mongrelize

cross-breed

verb
  • To breed separate strains of the same species in order to create new traits. 

  • To breed members of similar albeit distinct species, for example, horse X donkey = mule 

noun
  • An offspring produced by cross-breeding. 

adj
  • Of or pertaining to the offspring produced by cross-breeding. 

mongrelize

verb
  • To cross-breed 

  • To breed a mongrel 

How often have the words cross-breed and mongrelize occurred in a corpus of books? (source: Google Ngram Viewer )