identity vs synonym

identity

noun
  • The difference or character that marks off an individual or collective from the rest of the same kind; selfhood; the sense of who something or someone or oneself is, or the recurring characteristics that enable the recognition of such an individual or group by others or themself. 

  • An element of an algebraic structure which, when applied to another element under an operation in that structure, yields this second element. 

  • A well-known or famous person. 

  • A name or persona—a mask or appearance one presents to the world—by which one is known. 

  • An equation which always holds true regardless of the choice of input variables. 

  • Sameness, identicalness; the quality or fact of (several specified things) being the same. 

  • Any function which maps all elements of its domain to themselves. 

synonym

noun
  • A word whose meaning is the same as that of another word. 

  • An alternative (often shorter) name defined for an object in a database. 

  • Any name for a taxon, usually a validly published, formally accepted one, but often also an unpublished name. 

  • A word or phrase with a meaning that is the same as, or very similar to, another word or phrase. 

  • Any of the formal names for a taxon, including the valid name (i.e. the senior synonym). 

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