"Rock-a-bye Baby" may be an American nursery rhyme and lullaby, whose melody may be a variant of the English satirical ballad Lilliburlero. Originally titled "Hushabye Baby", this nursery rhyme was said to be the first poem written on American soil. Although there is no evidence as to when the lyrics were written, it may date from the 1600s. It is rumoured that it was written by a young pilgrim who sailed to America on the Mayflower. He was said to have observed the way native-American women rocked their babies in birch-bark cradles, which were suspended from the branches of trees, allowing the wind to rock the baby to sleep. However, the branches holding the cradles sometimes had a habit of breaking, causing the cradle to fall and the baby in it to get hurt. Rock-a-bye as a phrase apparently was first recorded in 1805. The nursery rhyme suggests a falling, apparently related to a terrible accident in 1706 where the Earl of Sandwich's son was tossed without warning from his cradle. The cradle was later found in the Thames River empty and alone.
Another source reports that Effie Crockett, a relative of Davy Crockett, wrote the lyrics in 1872 while babysitting a restless child.
In Derbyshire, England, local legend has it that the song relates to a local character in the late 1700s, Betty Kenny (Kate Kenyon), who lived with her charcoal-burner husband, Luke, and their eight children in a huge yew tree in Shining Cliff Woods in the Derwent Valley, where a hollowed-out bough served as a cradle. 
Yet another theory has it that the song, like "Lilliburlero", refers to events immediately preceding the "Glorious Revolution". The baby is supposed to be the son of King James II of England, who was widely believed to be someone else's child smuggled into the birthing room in order to provide a Catholic heir for James. The "wind" may be that political "wind" or force "blowing" or coming from the Netherlands bringing James' nephew and son-in-law, William III of England, a.k.a. William of Orange, who would eventually depose King James II in the revolution. The "cradle" is the House of Stuart Stuart monarchy.
The lyrics are:
Rock-a-bye baby, in the treetop,
When the wind blows, the cradle will rock,
When the bough breaks, the cradle will fall,
And down will come baby, cradle and all.
Only the words in the first four lines are supposed to be from the Pilgrim boy in America. Lines 5-12 are a later invention.
Alternate Lyrics as shown in The Real Mother Goose published in 1916:
Rock-a-bye, baby, thy cradle is green;
Father's a nobleman, mother's a queen;
And Betty's a lady, and wears a gold ring;
And Johnny's a drummer, and drums for the king.
 See also