Say some guy was a crook, though he didn’t look it, and he saw a chance to steal and took it: when the alarm went off he’d know he had to book it.
Wait, what? Book the alarm? Noooo… Although book it is a term perhaps more often known for use with tickets and other things that need to be reserved, it also has a slang use to refer to rather unreserved haste. “Man, he was bookin’ it around the corner, and he ran right into a cop!” It can also be speed of other activities: “Your essay’s due when? Six hours? Have you written it yet? Dude, you’d better book it!”
It’s an interesting usage, inasumch as books are not always thought of as fast-moving (jacket-flap reviews nothwithstanding). Boot it and boost it have clear senses, and cook it would seem a suitable metaphor (heat = speed); beat it is common enough, and of course move it. But book it? Librarians are known no more for celerity than for celebrity.
But, now, what are all these its? Well, they’re rather like what you might be muttering between breaths as you book it to something you’re late for: they’re expletives. That is to say, they just fill out the sentence. Originally (in the 16th century) there was always some sort of “it” in mind: fight it out meant “fight the matter out.” The out was soon enough dropped and the form became a pattern with an indefinite object. Shakespeare made use of this form several times.
This phrase does have a quick sound; it has the bursting [b] of book and the kick-back of the kit. (Speaking of kick, it’s also very similar to bucket; in northern British dialects, it may be a homophone.) When we look at it, we see the boo, which could be the scare that motivated the flight. The sequential circles of boo may also recall some cartoonish indications of motion. Book is a good old Anglo-Saxon four-letter word (those are so often suited to rushes), and it is even quicker – and thinner, and depersonalizing. No time to be nice! Shakespeare notwithstanding, this form has a colloquial feeling, and of course haste and slang go well together: it is not so dignified to move at top speed, and the use of an obviously casual form can reinforce the need not to stand on ceremony.
Where did this phrase come from? I don’t know; slang can be a prodigious borrower. I’m inclined to guess that it’s a reference to booking a ticket to somewhere. Truly fussy prescriptivists may be jogged to remember that this book is also a verbing, of the type that focuses on the destination of the act, and therefore must be an abomination unto the language (since at least AD 966).
But do people have that in mind when saying it? Most likely not. And I’m inclined to think that any of quite a few words would fit here, and people would still understand the intent. “It’s going to rain; we’ll really have to ___ it back home.” Fill in the blank: not every word will work – short ones are best – and it seems that verbed nouns suit especially well, but you could get away with quite a lot of words. You could practically throw a whole book at it!