keep from vs slip through the cracks

keep from

verb
  • To cause to be excluded or not present. 

  • To make and cause to remain secret. 

  • To protect or preserve from. 

  • To prevent or restrain (someone or something) from; to refrain or cause to refrain from. 

slip through the cracks

verb
  • To escape notice or lack sufficient attention. 

How often have the words keep from and slip through the cracks occurred in a corpus of books? (source: Google Ngram Viewer )