keel over vs nose-dive

keel over

verb
  • To collapse in a faint; to black out, to swoon. 

  • To die. 

  • Of a vessel: to roll so far on its side that it cannot recover; to capsize or turn turtle. 

nose-dive

How often have the words keel over and nose-dive occurred in a corpus of books? (source: Google Ngram Viewer )