Jack Frost is the elfin creature that we say has visited when we see the fine lace work of ice on our windows on a crisp frosty morning. He crisps the fallen leaves in autumn and makes mirrors from the puddles in spring.
The origins of Jack Frost go back as far in time as Viking folklore, the name coming from the Norse term "jokul frosti" meaning icicle frost. He was the son of the Nordic wind god Kari. He was known as an artistic sprite, traveling through villages in the night and decorating them with his ice art. This is the original version of our perception of him as an elfin creature.
Russian folk tales have the frost produced by a smith forging water chains for the earth, and parts of Russia give him a partner, Frostwoman, who with him controls the winter weather and must be placated. The German tradition has an old lady shaking out an eiderdown and in Australia the aboriginal tale is of the seven sisters of the Pleiades throwing ice daggers to the earth.
The depiction of Jack Frost as we in the west think of him was first popularized by the artist Thomas Nast in a picture published in Harper's Weekly in 1864. The picture, Central Park in winter, depicts Jack Frost as a creature covered in icicles, though perhaps not so elfin as we now see him. Thomas Nast is also responsible for many of our popular images of Santa Claus and Christmas.
Jack Frost was never really associated with Christmas, in the way that Santa Claus is, but more generally with the weather. This has been changing in recent years as Hollywood has used him as a character in several films, not always in a complimentary way. He is a serial killer in one (Jack Frost 1996, and a sequel), and in the 1998 film starring Michael Keaton he is the victim of a fatal accident on Christmas Eve. Most recently he appears in a film with Tim Allen (Santa Claus 3) where he attempts to take over the role of Father Christmas. Authors have long been wise to his appeal however, and he appears as a minor character and as a central part of several fantasy books.