admit vs keep back

admit

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

  • 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. 

keep back

verb
  • To restrict or restrain. 

  • To hold back; to refuse to give or share. 

  • To prevent (a pupil) from advancing in a course. 

  • To stay back; to refrain from approaching. 

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