let in vs permit

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). 

permit

verb
  • To allow (someone) to do something; to give permission to. 

  • To allow (something) to happen, to give permission for. 

  • To allow for, to make something possible. 

  • To allow, to admit (of). 

  • To grant formal authorization for (something). 

  • To attempt to obtain or succeed in obtaining formal authorization for (something). 

noun
  • A pompano of the species Trachinotus falcatus. 

  • An artifact or document rendering something allowed or legal. 

  • A learner's permit. 

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