backbreaker vs importunate

backbreaker

noun
  • A strenuous and exhausting task, typically involving physical effort. 

importunate

adj
  • Persistent or pressing, often annoyingly so. 

  • Given to importunate demands, greedily or thoughtlessly demanding. 

verb
  • To importune, or to obtain by importunity. 

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