expel vs let in

expel

verb
  • To eject or erupt. 

  • To remove from membership. 

  • To deport. 

let in

verb
  • To let someone or something come in; to admit someone or something in. 

  • To associate with. 

  • To divulge one's inner thoughts to (someone), making oneself emotionally vulnerable to them; to open up to (someone). 

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