Snap up is an idiom that means to buy or acquire something quickly. It can be used in a variety of contexts, such as when someone wants to purchase something before it is sold out or when someone wants to take advantage of a good deal. The term can be broken down into three parts: HOOK, GRAB, and NAB. HOOK is a four-letter word meaning to catch or attract with a bait or lure. GRAB is also a four-letter word meaning to take hold of suddenly and quickly. NAB is a three-letter word meaning to capture or seize. Together, these words form the phrase snap up, which means to acquire something quickly.