It cracked me up! see earlier discussion

Posted by Keith Rennie on December 03, 2004

In Reply to: It cracked me up! posted by Solaris on December 03, 2004

: I can't imagine a person cracking into pieces when they find something amusing - It certainly Wouldn't be amusing if it happened literally. There's also variations: "A good crack" or even "cracking jokes" which I would imagine is possibly related too.

: so, "what's the crack" with this one?
Crack that frozen face into a smile, friend, and scroll down to the many postings on "let's get cracking" beginning 19 November. I think "to crack up" meaning laugh hilariously is originally US but spread to Britain.