dirt vs obscenity

dirt

noun
  • Meanness; sordidness. 

  • A stain or spot (on clothes etc); any foreign substance that worsens appearance. 

  • Previously unknown facts, or the invented "facts", about a person. 

  • In placer mining, earth, gravel, etc., before washing. 

  • freckles 

  • Soil or earth. 

verb
  • To make foul or filthy; soil; befoul; dirty 

obscenity

noun
  • The qualities that make something obscene; lewdness, indecency, or offensive behaviour. 

  • Specifically, an offensive word; a profanity; a dirty word. 

  • An act of obscene behaviour. 

  • Something that is obscene. 

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