ascend vs flatten out

ascend

verb
  • To slope in an upward direction. 

  • To become higher in pitch. 

  • To move upward, to fly, to soar. 

  • To succeed. 

  • To trace, search or go backwards temporally (e.g., through records, genealogies, routes, etc.). 

  • To lose one's virginity, especially of a man through unpaid and consensual sexual intercourse with a woman. 

  • To go up. 

  • To rise; to become higher, more noble, etc. 

flatten out

verb
  • To win a fight, usually by punching someone until they are knocked over 

  • To make flat (something rough, folded or bumpy). 

  • To become more even. 

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