keep back vs uncover

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. 

uncover

verb
  • To show openly; to disclose; to reveal. 

  • To remove one's hat or cap as a mark of respect. 

  • To reveal the identity of. 

  • To expose the genitalia. 

  • To remove a cover from. 

  • To expose (lines of formation of troops) successively by the wheeling to right or left of the lines in front. 

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