keel over vs overbalance

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. 

overbalance

verb
  • To lose one's balance; to fall over. 

  • To throw (someone or something) off balance; to cause to capsize. 

  • To be more important than; to outweigh. 

  • To cause an imbalance in (something) by means of excess weight or numbers. 

noun
  • Excess of weight or value; something more than an equivalent. 

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