black mark vs onus

black mark

noun
  • something that negatively affects someone's reputation 

onus

noun
  • Stigma. 

  • A legal obligation. 

  • Burden of proof, onus probandi. 

  • Blame. 

  • Responsibility; burden. 

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