complexity vs severity

complexity

noun
  • That which is and renders complex; intricacy; complication. 

  • The state of being complex; intricacy; entanglement. 

severity

noun
  • The degree of something undesirable; badness or seriousness. 

  • The state of being severe. 

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