Lucky you! You just won the lottery and your windfall will make life very comfortable for you and your family. A windfall is a crazy bit of unexpected good fortune.
First used in the fifteenth century, the word windfall originally referred to fruit that the wind blew from the trees. Like a prize was there for whomever found it — no need for the ladder and effort of picking it from the tall trees. The word eventually came to mean any unexpected and easily-gained good fortune, typically one involving money, such as the windfall profit from a lucky stock purchase.