Another in a long line of well intended
admonitions that parents use with small children. It is meant to
put a smile on a child's face at
bedtime and encourage them to
snuggle up and go to sleep. Instead this warning about unseen insects that may or
may not be in their bed, about to chew on them, often
backfires.
Try telling your 6 year old nephew you were just kidding. And no, they do not know what a euphemism is at that age.
Don't tell a child this on the same night that you have them sing these lines:
and if I die, before I wake...