prevent vs warn

prevent

verb
  • To stop (an outcome); to keep from (doing something). 

warn

verb
  • To advise or order to go or stay away. 

  • To notify or inform (someone, about something). 

  • To caution or admonish (someone) against unwise or unacceptable behaviour. 

  • To give warning. 

  • To summon (someone) to or inform of a formal meeting or duty. 

  • To make (someone) aware of impending danger, evil, etc. 

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