imbrue vs impregnate

imbrue

verb
  • To stain (in, with, blood, slaughter, etc.). 

impregnate

verb
  • To saturate, or infuse. 

  • To fill pores or spaces with a substance. 

  • To fertilize. 

  • To cause to become pregnant. 

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