Thing vs convention

Thing

noun
  • Nickname or appellative for numerous "things", including fictional characters. 

  • A public assembly or judicial council in a Germanic country. 

  • Nickname for the Volkswagen 181. 

convention

noun
  • A formal agreement, contract, rule, or pact. 

  • A treaty or supplement to such. 

  • A meeting or gathering. 

  • A practice or procedure widely observed in a group, especially to facilitate social interaction; a custom. 

  • The convening of a formal meeting. 

  • A formal deliberative assembly of mandated delegates. 

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