pronoun vs synonymum

pronoun

noun
  • A type of word that refers anaphorically to a noun or noun phrase, but which cannot ordinarily be preceded by a determiner and rarely takes an attributive adjective. 

  • Any of the pronouns by which a person prefers to be described, typically reflecting gender identity. 

synonymum

noun
  • Synonym. 

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