book it

The word book as a verb has many meanings, one of which is “to record or register” something, such as officially placing a bet on the books. This sense is found as early as the 1200s. In the 1700–1800s, the meaning of book expanded to “reserving” something generally, such as a table at a restaurant, e.g., I booked it for 7:00 pm.

Book it for “running away quickly” originates in the 1930s Black slang expression bookity-book, meaning to imitate all the noise of scampering away.

By the 1950s, bookity-book was apparently shortened to book and took on the meaning of “to move quickly” in youth slang. This sense, it has been suggested, was influenced by boogie, slang for “move.” In the 1960s, the specific phrase book it emerged for “fleeing a scene,” usually on foot and to evade getting in trouble, with the it sometimes dropped, e.g., We gotta book.

As early as the 1700s, book it has been used to mean “study intensely,” not unlike hit the books.

Another slang sense of book it draws on betting books, where sports bets and other wagers are recorded. Book it, here, has the sense of “bet on it” or “you can bet on it” (write it down in the betting book). The phrase is used both to refer to actual bets but also to more metaphorical assurances and predictions. Using book as a verb for “writing a bet down in a book” dates back to the 1800s.