expatiate vs sound off

expatiate

verb
  • To write or speak at length; to be copious in argument or discussion. 

  • To range at large, or without restraint. 

sound off

verb
  • To hold forth about something in an opinionated manner. 

  • Command instructing a person to confirm that they are present or that some other objective has been met. 

  • Command instructing a person to speak up or acknowledge something. 

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