blog vs commentary

blog

noun
  • A website that allows users to reflect, share opinions, and discuss various topics in the form of an online journal, sometimes letting readers comment on their posts. Most blogs are written in a slightly informal tone (personal journals, news, businesses, etc.) 

  • An individual post to a blog. 

verb
  • To contribute to a blog. 

  • To blag, to steal something; to acquire something illegally. 

commentary

noun
  • A series of comments or annotations; especially, a book of explanations or expositions on the whole or a part of some other work. 

  • An oral relation of an event, especially broadcast by television or radio, as it occurs. 

  • A brief account of transactions or events written hastily, as if for a memorandum. 

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