pen in vs run to ground

pen in

verb
  • To cause to be stuck in a situation; to be forced into a situation by circumstances. 

  • To enclose (animals) in a pen. 

  • To schedule; fix a date for. 

run to ground

verb
  • Synonym of run to earth 

How often have the words pen in and run to ground occurred in a corpus of books? (source: Google Ngram Viewer )