Hush, little baby is an American lullaby - that is, a folk song designed to help children fall asleep. As with most folk songs, the original author is unknown, and many variations of the lyrics exist, including some that have been incorporated into copyrighted songs. A popular variant goes:

Hush, little baby, don't say a word

Mama's gonna buy you a mockin'bird

If that mockin'bird don't sing

Mama's gonna buy you a diamond ring

If that diamond ring turns brass,

Mama's gonna buy you a looking glass

If that looking glass gets broke

Mama's gonna buy you a billy goat

If that billy goat don't pull,

Mama's gonna buy you a cart and mule

If that cart and mule turn over,

Mama's gonna buy you a dog named Rover

If that dog named Rover won't bark,

Mama's gonna buy you a horse and cart

If that horse and cart fall down,

Then you'll be the sweetest little baby in town