gold rush vs windfall

gold rush

noun
  • A feverish obsession with seeking profits, especially in new markets. 

  • Any period of feverish migration into an area in which gold has been discovered. 

  • A cocktail made from bourbon, honey, and lemon juice. 

  • The urge to win gold medals, as in the Olympic Games. 

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 gold rush and windfall occurred in a corpus of books? (source: Google Ngram Viewer )