eye-apple vs ken

eye-apple

noun
  • The eyeball or pupil 

  • Synonym of apple of one's eye 

ken

noun
  • Knowledge, perception, or sight. 

  • Youth or children's group. 

  • A Japanese unit of length equal to six shakus 

  • Range of sight. 

  • The tsurugi 

verb
  • To know, perceive or understand. 

How often have the words eye-apple and ken occurred in a corpus of books? (source: Google Ngram Viewer )