accede vs make valid

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). 

make valid

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