Oxford English Dictionary, 2nd ed. (online version, accessed Jan. 27, 2009), entry for "Castle", def. 9. "Chess. One of the pieces, made to represent a castle; also called a ROOK.". New Oxford American Dictionary, 2nd ed. (2005) says that "castle" is informal and an "old-fashioned term for rook". The Oxford Companion to Chess, by David Hooper & Kenneth Whyld, 2nd ed. (1992), p. 344 says "In English-speaking countries non-players sometimes call it a castle...". Let's Play Chess by Bruce Pandolfini (1986) p. 30, says "The rook is the piece mistakenly called the castle."; The Everything Chess Basics Book by Peter Kurzdorfer and the United States Chess Federation, Adams Media 2003, page 30, says "... often incorrectly referred to as a castle by the uninitiated".
