keep one's nose to the grindstone vs toil

keep one's nose to the grindstone

toil

noun
  • Trouble, strife. 

  • Labour, work, especially of a grueling nature. 

  • A net or snare; any thread, web, or string spread for taking prey. 

verb
  • To struggle. 

  • To labour; work. 

  • To weary through excessive labour. 

  • To work (something); often with out. 

How often have the words keep one's nose to the grindstone and toil occurred in a corpus of books? (source: Google Ngram Viewer )