request vs whistle for

request

verb
  • To ask for (something). 

  • To ask (somebody) to do something. 

noun
  • A message sent over a network to a server. 

  • Act of requesting (with the adposition at in the presence of possessives, and on in their absence). 

  • Condition of being sought after. 

  • A formal message requesting something. 

whistle for

verb
  • To ask for with no chance of success. 

  • Used other than figuratively or idiomatically: see whistle, for. 

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