confine vs pen in

confine

verb
  • To restrict (someone or something) to a particular scope or area; to keep in or within certain bounds. 

noun
  • Confinement, imprisonment. 

  • A boundary or limit. 

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. 

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