converse vs underside

converse

noun
  • The opposite or reverse. 

  • Free verbal interchange of thoughts or views; conversation; chat. 

  • One of a pair of terms that name or describe a relationship from opposite perspectives; converse antonym; relational antonym. 

  • Of a proposition or theorem of the form: given that "If A is true, then B is true", then "If B is true, then A is true.". 

verb
  • To keep company; to hold intimate intercourse; to commune. 

  • To talk; to engage in conversation. 

adj
  • opposite; reversed in order or relation; reciprocal 

underside

noun
  • The side that is below or underneath, the bottom. 

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