fall behind vs get to

fall behind

verb
  • Used other than figuratively or idiomatically: see fall, behind. 

  • To be late (for a regular event) 

  • To be progressively below average in performance. 

  • to fail to keep up (with) 

get to

verb
  • To be allowed to. 

  • To reach or arrive at (a physical or abstract destination, or state of doing a certain activity). 

  • To affect adversely; to upset or annoy. 

  • To intimidate. 

  • To go to or be located at (a particular place). 

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