leap to mind vs occur

leap to mind

verb
  • To appear suddenly in one's thoughts. 

occur

verb
  • To come or be presented to the mind; to suggest itself. 

  • To happen or take place. 

  • To present or offer itself. 

  • To be present or found. 

How often have the words leap to mind and occur occurred in a corpus of books? (source: Google Ngram Viewer )