Turn up for the book

Q From Laura F Spira: I wonder if you can help with a query: what is the origin of the expression a turn up for the book, presumably indicating an unexpected outcome, a surprise?

A It now means exactly what you say, something surprising. The origin is in horse racing, where the book was the record of bets laid on a race kept by — who else — a bookmaker. So when a horse performed in a way that nobody expected, so that most bets lost, it was something that benefited the book and so the bookmaker. The classic example would be a rank outsider that won with few bets on it, netting the bookmaker a nice windfall profit.