admit vs let in

admit

verb
  • To allow to enter; to grant entrance (to), whether into a place, into the mind, or into consideration 

  • To give warrant or allowance, to grant opportunity or permission (+ of). 

  • To allow (someone) to enter a profession or to enjoy a privilege; to recognize as qualified for a franchise. 

  • To concede as true; to acknowledge or assent to, as an allegation which it is impossible to deny (+ to). 

  • To allow to enter a hospital or similar facility for treatment. 

  • To be capable of; to permit. In this sense, "of" may be used after the verb, or may be omitted. 

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