Book Move

Book is Old English boc, generally traced to a root meaning “beech,” from the notion of beechwood tablets on which runes were inscribed; Etymonline also records the idiom “by the book,” “according to the rules,” from the 1590s, which is exactly the force of the chess phrase. A book move is an opening move found in standard reference books on opening theory; a game is “in book” while both players follow known references and “out of book” once a player deviates. The term relates to the era when nearly all opening theory was contained only in books — Modern Chess Openings, first published in 1911, has had fifteen revisions. The genre is older still: the prototype was the German Handbuch des Schachspiels (the “Bilguer Handbuch”), first published in 1843, which pioneered the use of theory tables and remained a standard reference until the emergence of MCO in the early twentieth century.

First documented: 1843 — Handbuch des Schachspiels (“Bilguer Handbuch”), 1843 — origin of the opening-book genre the phrase refers to; the phrase “book move” itself is undated