accede vs sign off on

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). 

sign off on

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