probity vs skulduggery

probity

noun
  • Integrity, especially of the quality of having strong moral principles; decency and honesty. 

skulduggery

noun
  • A devious device or trick. 

  • Dishonest, underhanded, or unscrupulous activities or behaviour. 

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