"Rock-a-bye Baby" was an Earth lullaby.
In 1941, Nancy sang it to Jenkins, who had become infected with the Empty Child plague. She continued to sing at the Ninth Doctor's request to keep Jenkins sleeping as the Doctor freed her from her handcuffs. (TV: The Empty Child [+]Loading...["The Empty Child (TV story)"])
Jasper Adeola sang it to his daughter Tanya Adeola. (PROSE: The Stone House [+]Loading...["The Stone House (novel)"])
The song went:
Rock-a-by baby,
On the tree tops.
When the wind blows,
The cradle will rock.
When the bough breaks,
The cradle will fall,
And down will come baby,
Cradle and all.
(TV: The Empty Child [+]Loading...["The Empty Child (TV story)"])