graffiti vs impregnate

graffiti

verb
  • To mark a surface with such images. 

noun
  • Drawings or words drawn on a surface in a public place, usually made without authorization. 

  • Informal inscriptions, figure drawings, etc., as opposed to official inscriptions. 

impregnate

verb
  • To fill pores or spaces with a substance. 

  • To saturate, or infuse. 

  • To fertilize. 

  • To cause to become pregnant. 

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