appertain vs pertain

appertain

verb
  • To belong as a part, right, possession, attribute, etc. 

  • To belong to or be a part of, whether by right, nature, appointment, or custom; to relate to. 

pertain

verb
  • To belong to or be a part of; be an adjunct, attribute, or accessory of. 

  • To apply; to be or remain in place; to continue to be applicable. 

  • To relate, to refer, be relevant to. 

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