espy vs peep out

espy

verb
  • To find out or observe (someone or something, especially if not easy to see) by spying or looking; to catch sight of; to see; to spot. 

  • To see (someone or something) without foreplanning or unexpectedly. 

peep out

verb
  • to show, to be visible. 

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