ideogram vs rune

ideogram

noun
  • A picture or symbol which represents the idea of something without indicating the sequence of sounds used to pronounce it. Examples include digits, traffic signs, and graphic symbols such as @. 

rune

noun
  • A letter or mark used as a mystical or magic symbol. 

  • A letter, or character, used in the written language of various ancient Germanic peoples, especially the Scandinavians and the Anglo-Saxons. 

  • A Finnish or Scandinavian epic poem, or a division of one, especially a division of the Kalevala. 

  • A verse or song, especially one with mystical or mysterious overtones; a spell or an incantation. 

  • A Unicode code point. 

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