The words and origin of the "Rock a bye baby/Hush a bye baby" rhyme are said to have originated from America. It was the practice of some Native Americans to place a baby in the branches of a tree allowing the wind to gently rock the child to sleep "Hush a bye baby on the treetop". The meaning to the words of the song "Hush a bye baby" seem to match this explanation. The words to the "Hush a bye baby" song have the intention of making a child sleep it can therefore be correctly described as both a nursery rhyme and a lullaby! The words to the "Hush a bye baby" song were first published in 1765.
Another theory is that the song refers to events immediately preceding the Glorious Revolution of 1688, the overthrow of King James II of England aka James VII of Scotland. The baby is supposed to be the son of James VII and II, 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 the 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 royal House of Stuart.