means To make a sudden sharp sound or movement — a quick crack, break, bite, or finger-click — or, by extension, to lose one's composure all at once.

from An echo word: 'snap' came into English in the 1400s–1500s from the Dutch or Low German 'snappen,' meaning to bite or seize suddenly. It's onomatopoeic at heart — the word is built to sound like the brisk crack it names, a cousin of 'snip,' 'snub,' and the eager 'snack' (also 'a bite'). From the literal bite came every later snap: the breaking twig, the dog's jaws, the camera shutter, and the temper that gives way without warning.