When I was little and sang this song to my baby brother, I imagined the cradle was hung on a very low branch, just inches above the ground (ignoring the words “tree top”), because otherwise the baby was going to be horribly injured. Wikipedia’s explanations were not entirely satisfying.
Mother Goose Quiltie Pattern #16
Rock-a-bye Baby in the tree top,
When the wind blows, the cradle will rock;
When the bough breaks, the cradle will fall,
And down will come baby, cradle and all.
“A bough seems a kind of funny place to hang a cradle, even if the wind will rock it and save baby’s sister the work of caring for it. A nice square on your quilt is a much safer place, ’cause babies are too nice to let them tumble down from treetops.”