The Cauldron is drawn from ancient Celtic mythology, and is sometimes called the Cup or Cauldron of Cerridwen. The ancient Celts used cauldrons for food and in ritual as an emblem of abundance and divine inspiration. In Celtic mythology and folklore, the cauldron provides infinite sustenance or artistic inspiration.

As a Wiccan ritual tool, it is mostly symbolic. Most often used to represent the fire or water elements, the cauldron is sometimes employed for scrying, for mixing herbs, for consecration, or to hold the ingredients for a spell. It is generally held to be a feminine symbol:

From: about.com