Genesis 21:3

And Abraham called the name of his son that was borne unto
him, whom Sarah bare to him, Isaac.
] Which is the name he was directed to give him, ( Genesis 17:19 ) ; and he remembers the order, and is obedient to it; the reason of which name, which signifies laughter, was on account of his laughing for joy at the promise made him, as well as there might be afterwards a further reason for it, from Sarah's laughing through distrust; and it might presignify the joy and laughter that would be expressed by others at his birth; and perhaps also that he would be the object of the laughter and derision of his brother; such a number of events agreeing with his name.