go to ground vs keep out of sight

go to ground

verb
  • To fall on the floor 

  • To escape into a burrow, hole, etc. when being hunted. 

  • To hide from public view or sequester oneself, especially when authorities, members of the news media, or others are looking for one. 

keep out of sight

How often have the words go to ground and keep out of sight occurred in a corpus of books? (source: Google Ngram Viewer )