appear vs occur

appear

verb
  • To come or be in sight; to be in view; to become visible. 

  • To come before the public. 

  • To become visible to the apprehension of the mind; to be known as a subject of observation or comprehension, or as a thing proved; to be obvious or manifest. 

  • To bring into view. 

  • To stand in presence of some authority, tribunal, or superior person, to answer a charge, plead a cause, etc.; to present oneself as a party or advocate before a court, or as a person to be tried. 

  • To seem; to have a certain semblance; to look. 

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 appear and occur occurred in a corpus of books? (source: Google Ngram Viewer )