abend vs fall down

abend

verb
  • To terminate abnormally. 

noun
  • The abnormal termination of a program. 

  • Termination of a process prior to completion. 

fall down

verb
  • To fail. 

  • To sail or drift toward the mouth of a river or other outlet. 

  • To fall to the ground. To collapse. 

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