拟声词。
At their head, apart from the rest, was a black bull, who appeared to be their leader; he came roaring along, his tail straight an end, and at times tossing up the earth with his horns. I never felt such a desire to have a crack at any thing in all my life. He drew nigh the place where I was standing; I raised my beautiful Betsey to my shoulder, took deliberate aim, blazed away, and he roared, and suddenly stopped. ["A Narrative of the Life of David Crockett, Written by Himself," Philadelphia, 1834]Adjectival meaning "top-notch, superior" (as in a crack shot) is slang from 1793, perhaps from earlier verbal sense of "do any thing with quickness or smartness" (Johnson). Grose (1796) has "THE CRACK, or ALL THE CRACK. The fashionable theme, the go." To fall through the cracks figuratively, "escape notice," is by 1975.