mean to say vs speak for

mean to say

verb
  • To imply or intend to convey with one's words; used to correct or clarify one's previous utterance, or to seek such clarification. 

speak for

verb
  • Used other than figuratively or idiomatically: see speak, for. 

  • To represent an intrinsic quality 

  • To claim, reserve, or occupy. 

  • To speak on somebody's behalf. 

How often have the words mean to say and speak for occurred in a corpus of books? (source: Google Ngram Viewer )