darken vs graffiti

darken

verb
  • To make dark or darker in colour. 

  • To become gloomy, darker in mood. 

  • To render gloomy, darker in mood. 

  • To cloud, obscure, or perplex; to render less clear or intelligible. 

  • To become dark or darker (having less light). 

  • To make dark or darker by reducing light. 

  • To blind, impair the eyesight. 

  • To become dark or darker in colour. 

  • To be blinded, lose one’s eyesight. 

  • To make foul; to sully; to tarnish. 

  • To get dark (referring to the sky, either in the evening or as a result of cloud). 

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 darken and graffiti occurred in a corpus of books? (source: Google Ngram Viewer )