accede vs invalidate

accede

verb
  • To become a party to an agreement or a treaty. 

  • To agree or assent to a proposal or a view; to give way. 

  • To come to an office, state or dignity; to attain, assume (a position). 

invalidate

verb
  • To make invalid. Especially applied to contract law. 

  • To make or declare (an argument, statement, or theory) unsound or erroneous; disprove. 

  • To render invalid; discredit. 

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