To crack up

[Compaq]

That's an expression I'm not very fond of. It may be because I don't really get where it comes from. When you're cracking up, are you cracking like a fire? When a fire cracks, it sparks and sends out stuff that too often seem to be going straight for your eyes Is that the same sort of cracking? A fire might sound like some inner feeling of positive emotion that simply must burst out, often in laughter, hard breathing through nose or, if you're sick, a heavy cough attack. The expression could be referencing to the cracking of rock. Some forces far beyond the grasp of the average life form from deep inside the rock makes it crack. The rock simply must crack, it has no choice, because the force is acting out - the expression could be based on that. Or, perhaps it's the same as "to suit up": put on a suit? To crack up would then be to ingest crack, which would make us light headed and strongly sensitive to sounds and noise or sudden movement and stuff - except we were subject to sudden humour and didn't manage to keep our mask.

At the end of the day, I don't think I ever crack up. If anything, I crack down.

 

[Forkie]

I thought it was just an alternative to "splitting my sides"?

"I'm cracking up with laughter" = "My sides are splitting with laughter".