This is related to ancient superstitions that whistling indoors can lead to financial losses.
There was a belief that a "whistled" wind could burst into the house and take away all accumulated wealth. Whistling is akin to the wind, which has been viewed with caution since ancient times, as it is capable of destruction.
It is unknown how true this is, but the saying "don't whistle — there won't be any money" has been passed down from generation to generation.
Additionally, it is possible that a child's whistle is too loud and sharp, which may cause dissatisfaction among neighbors.
