split one's sides

Split′ting, very severe: very rapid.—Split on a rock, to meet some unforeseen and disastrous difficulty, to go to ruin; Split one's sides, to laugh immoderately; Split the difference, to divide equally the sum or matter in dispute, to take the mean.

Heidt's friends, too, proved most entertaining company, especially the one who, it appeared, was a poet; he had a store of anecdotes to make one split one's sides with laughing, and Heidt himself was in high spirits.

The poor little rocking-chair over in the corner was in reality a mere attempt at a rocking-chair; with the smallest sense of humour, one might easily split one's sides with laughter at it.