fend off vs let in

fend off

verb
  • To defend against; to repel with force or effort 

  • To prevent (a vessel) from running against anything with too much violence. 

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 fend off and let in occurred in a corpus of books? (source: Google Ngram Viewer )