forum vs marketplace

forum

noun
  • A square or marketplace in a Roman town, used for public business and commerce. 

  • A gathering for the purpose of discussion. 

  • A place for discussion. 

  • An Internet message board where users can post messages regarding one or more topics of discussion. 

  • A form of discussion involving a panel of presenters and often participation by members of the audience. 

marketplace

noun
  • An open area in a town housing a public market. 

  • A place or sphere for the exchange of anything, such as ideas or fashions. 

  • The world of commerce and trade. 

  • The space, actual or metaphorical, in which a market operates. 

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