'side-splitting' originates from the English words 'side' and 'split,' where 'side' refers to the sides of the body and 'split' means to break or crack, metaphorically describing intense laughter.

The term 'side-splitting' has been used in English since the 19th century to describe something extremely funny.

Initially, it meant 'causing laughter so intense it feels like one's sides might split,' and this meaning has largely remained the same in modern usage.