"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)
Jasper Adeola sang it to his daughter Tanya Adeola. (PROSE: The Stone House)
The song went: