castling vs keep

castling

noun
  • 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. 

  • 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). 

keep

noun
  • The main tower of a castle or fortress, located within the castle walls. 

  • The state of being kept; hence, the resulting condition; case. 

  • A cap for holding something, such as a journal box, in place. 

  • The food or money required to keep someone alive and healthy; one's support, maintenance. 

verb
  • To supply with necessities and financially support (a person). 

  • To refrain from freely disclosing (a secret). 

  • To continue in (a course or mode of action); to not intermit or fall from; to uphold or maintain. 

  • To remain edible or otherwise usable. 

  • To remain in a state. 

  • To observe; to adhere to; to fulfill; to not swerve from or violate. 

  • To raise; to care for. 

  • To have habitually in stock for sale. 

  • To act as wicket-keeper. 

  • To enter (accounts, records, etc.) in a book. 

  • To maintain the condition of; to preserve in a certain state. 

  • To restrain. 

  • To maintain (an establishment or institution); to conduct; to manage. 

  • To watch over, look after, guard, protect. 

  • To maintain possession of. 

  • To record transactions, accounts, or events in. 

  • To remain faithful to a given promise or word. 

  • To continue. 

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