dirty laundry vs graffiti

dirty laundry

noun
  • Unflattering or embarrassing facts, or questionable activities that one wants to remain secret, but which someone else may use as blackmail. 

  • Used other than figuratively or idiomatically: see dirty, laundry. 

  • A clothes hamper or other container in which soiled laundry is placed. 

graffiti

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. 

verb
  • To mark a surface with such images. 

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