hack it vs whistle past the graveyard

hack it

verb
  • To cope; to be successful in something despite adversity. 

  • Used other than figuratively or idiomatically: see hack, it. 

whistle past the graveyard

verb
  • To attempt to stay cheerful in a dire situation; to proceed with a task, ignoring an upcoming hazard, hoping for a good outcome. 

  • To enter a situation with little or no understanding of the possible consequences. 

How often have the words hack it and whistle past the graveyard occurred in a corpus of books? (source: Google Ngram Viewer )