ideogram vs insignia

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 @. 

insignia

noun
  • A symbol or token of personal power, status, or office, or of an official body of government or jurisdiction. 

  • A patch or other object that indicates a person's official or military rank, or membership in a group or organization. 

  • A mark or token by which anything is known. 

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