castle vs mansion

castle

noun
  • A large residential building or compound that is fortified and contains many defences; in previous ages often inhabited by a nobleman or king. Also, a house or mansion with some of the architectural features of medieval castles. 

  • An instance of castling. 

  • The wicket. 

  • A defense structure in shogi formed by defensive pieces surrounding the king. 

  • A rook; a chess piece shaped like a castle tower. 

verb
  • To house or keep in a castle. 

  • To create a similar defensive position in Japanese chess through several moves. 

  • To protect or separate in a similar way. 

  • To bowl a batsman with a full-length ball or yorker such that the stumps are knocked over. 

  • To move the king 2 squares right or left and, in the same turn, the nearest rook to the far side of the king. The move now has special rules: the king cannot be in, go through, or end in check; the squares between the king and rook must be vacant; and neither piece may have been moved before castling. 

mansion

noun
  • A large house or building, usually built for the wealthy. 

  • An astrological house; a station of the moon. 

  • An apartment building. 

  • One of twenty-eight sections of the sky. 

  • An individual habitation or apartment within a large house or group of buildings. (Now chiefly in allusion to John 14:2.) 

  • Any of the branches of the Rastafari movement. 

  • A luxurious flat (apartment). 

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