Pop vs lad's love

Pop

noun
  • The body of college prefects. 

  • A popular classical music concert. 

  • A social club and debating society at Eton College. 

name
  • Traditional nickname for a stage doorman. 

lad's love

noun
  • southernwood 

How often have the words Pop and lad's love occurred in a corpus of books? (source: Google Ngram Viewer )