pen in vs wall in

pen in

verb
  • To enclose (animals) in a pen. 

  • To schedule; fix a date for. 

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

wall in

verb
  • To enclose by surrounding with walls. 

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