<Dd> Though baby sleeps, he hears what she sings </Dd> <Dl> <Dd> Rock - a-bye baby, do not you fear </Dd> <Dd> Never mind, baby, mother is near </Dd> <Dd> Wee little fingers, eyes are shut tight </Dd> <Dd> Now sound asleep - until morning light </Dd> </Dl> <Dd> Rock - a-bye baby, do not you fear </Dd> <Dd> Never mind, baby, mother is near </Dd>

Where does rock a bye baby come from