idea vs mnemonic

idea

noun
  • An image of an object that is formed in the mind or recalled by the memory. 

  • An abstract archetype of a given thing, compared to which real-life examples are seen as imperfect approximations; pure essence, as opposed to actual examples. 

  • A conception in the mind of something to be done; a plan for doing something, an intention. 

  • A purposeful aim or goal; intent 

  • A musical theme or melodic subject. 

  • More generally, any result of mental activity; a thought, a notion; a way of thinking. 

  • A vague or fanciful notion; a feeling or hunch; an impression. 

mnemonic

noun
  • Something (especially a series of ideas, letters, words, etc.) used to help in remembering a thing; a memory aid. 

  • The human-readable, textual form of an assembly language instruction, not including operands. 

adj
  • Of or relating to memory. 

  • Especially of a series of ideas, letters, words, etc.: intended to help in remembering. 

  • Of or relating to mnemonics (“the study of techniques for remembering anything more easily”). 

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