flatten out vs unwrinkle

flatten out

verb
  • To make flat (something rough, folded or bumpy). 

  • To win a fight, usually by punching someone until they are knocked over 

  • To become more even. 

unwrinkle

verb
  • To stop being wrinkly; to become flat or smooth. 

  • To remove wrinkles from. 

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