mid-15c., past participle adjective from crack (v). Meaning "mentally unsound" is 17c. (cf. crack-brain "crazy fellow"). The equivalent Greek word was used in this sense by Aristophanes.
Said; praised •Most often in the negative: This beer ain't all it's cracked up to be
[1836+; fr 1300s sense of crack, ''boast, brag'']
Crazy; eccentric: You're cracked if you think I'll stay now (1692+)
get one's nuts