forebode vs prewarn

forebode

verb
  • To be prescient of (some ill or misfortune); to have an inward conviction of, as of a calamity which is about to happen; to augur despondingly. 

  • To predict a future event; to hint at something that will happen (especially as a literary device). 

prewarn

verb
  • To warn beforehand; to forewarn. 

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