castling vs swap

castling

noun
  • One that is cast. 

  • A miniature cast or mould. 

  • The act of constructing a defense structure in Japanese chess in which the king (玉) is positioned in a certain way so that it is protected by pawns (歩) and silver general(s) (銀) and/or gold general(s) (金) often with an additional knight (桂) and lance (香車). 

  • A move in which the king moves two squares towards a rook, and the rook moves to the other side of the king; the action of the verb to castle. 

swap

verb
  • To exchange or give (something) in an exchange (for something else). 

noun
  • An exchange of two comparable things. 

  • A financial derivative in which two parties agree to exchange one stream of cashflow against another stream. 

  • A social meal at a restaurant between two university societies, usually involving drinking and banter; commonly associated with fining and pennying; equivalent to a crewdate at Oxford University. 

  • Space available in a swap file for use as auxiliary memory. 

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