Middle English craken, from Old English cracian "make a sharp noise, give forth a loud, abrupt sound," from Proto-Germanic *krakojan (source also of Middle Dutch craken, Dutch kraken, German krachen); the whole group is probably ultimately imitative. Related: Cracked; cracking.

From c. 1300 as "burst, split open" (intransitive), also transitive, "cause to break into chinks." From 1785 as "break or crush into small pieces." Of the voice, "change tone suddenly," as that of a youth passing into manhood, c. 1600. The meaning "open and drink" (a bottle) is from 16c.

From early 14c. as "utter, say, speak, talk freely," especially "speak loudly or boastingly" (late 14c.). To crack a smile is from 1835, American English; to crack a joke is by 1732, probably from the "speak, say" sense. To crack the whip in the figurative sense is from 1886. To get cracking "go to work, start doing what is to be done" is by 1937.

What is a crack in English? A chat! The synonym is as perfect as possible; yet the words are subtly distinguished by a whole hemisphere of feeling. A chat, by comparison "wi' a crack," is a poor, frivolous, shallow, altogether heartless business. A crack is, indeed, only adequately to be defined as a chat with a good, kindly, human heart in it .... [P.P. Alexander, notes to "Last Leaves," Edinburgh, 1869]

"chest for keeping food or valuables" safe from risk of theft or fire, early 15c., save, from French en sauf "in safety," from sauf (see safe (adj.)). Spelling with -f- is by 1680s, from influence of safe (adj.).