stroke of fortune vs windfall

stroke of fortune

noun
  • Synonym of stroke of luck 

windfall

noun
  • A sudden large benefit; especially, a sudden or unexpected large amount of money, as from lottery or sweepstakes winnings or an unexpected inheritance or gift. 

  • Something that has been blown down by the wind. 

  • A fruit that has fallen from a tree naturally, as from wind. 

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