Nonsensical Lullabyes

Rrrrr...why does it have to take B an hour to fall asleep? I've always wondered why some nursery rhymes are so wicked. The famous lullabye for example:

Rock-a-bye-baby On the treetop
When the wind blows,
The cradle will rock.
When the bough breaks,
The cradle will fall
And down will come baby
Cradle and all

The best answer I got was:

"The author of this well-loved lullaby was reportedly a pilgrim who sailed on the Mayflower. The Wampanoag Indians, who befriended the colonists, carried their infants in cradleboards on their backs. In temperate weather, they suspended the cradles from tree limbs so that passing breezes could rock the babies while their mothers tended the maize and beans. With typical motherly indulgence, the cradles were decorated with shells, beads and porcupine quills. For sober-minded puritans, the sight of a birch tree festooned with such cradles must have been very memorable indeed. "

I'm trying to understand the wicked part where the bough (branch) breaks and the baby and cradle fall because if I took it literally, I could totally relate to the author and sometimes wouldn't mind if Breanna fell. Urgh! lol