ideogram vs numeral

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 @. 

numeral

noun
  • A representation of a number composed of such symbols. 

  • A number word, a simple or compound word for a number often having particular grammatical attributes depending on the language. 

  • A symbol that is not a word and represents a number, such as the Arabic numerals 1, 2, 3 and the Roman numerals I, V, X, L. 

  • A card whose rank is a number (usually including the ace as 1). 

adj
  • Of or relating to numbers; numerical. 

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