befoul vs graffiti

befoul

verb
  • To stain or mar (for example with infamy or disgrace). 

  • To entangle or run against so as to impede motion. 

  • To make foul; to soil; to contaminate, pollute. 

  • To defecate on, to soil with excrement. 

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. 

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