The Cailleach is the old Hag of Winter in the Celtic lands of the British Isles. Her name literally means ‘Hag’, though it originally came from a word meaning ‘Veiled One’. She is said to rule the winter months and the weather. She is often associated with Brigid, either trading off with Her when summer or spring comes, or by holding Brigid prison and releasing Her in spring.
She is associated with mountains and stone, and in some stories is a giantess—stones that fell out of Her apron were said to have formed the stone circles of those lands. In some traditions She comes out of Her hut on Brigid’s Day (Imbolc, February 1st) to gather firewood; if the day is a sunny one, She gathers a lot, and it is a sign that winter will be long (and yes, this is related to the American tradition about the groundhog, on Groundhog Day, though it’s a bit convoluted as it goes through the Pennsylvania Dutch).
In other stories She is said to have created the mountains Herself.
I've done another version of the Cailleach for the World Goddess Oracle, here.
This design is available on prints through Society6.