settle down vs settle in

settle down

verb
  • To get comfortable with one's new accommodation or circumstances. 

  • To become quiet and calm after a period of disturbance or restlessness. 

  • To establish a settled lifestyle, and especially to marry. 

settle in

verb
  • To get comfortable or established, as in a new place. 

  • Used other than figuratively or idiomatically: see settle, in. 

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