Colcannon is a traditional Irish Halloween dish. In Irish it’s known as cál ceannann meaning white-headed cabbage. There are some old traditions which revolve around colcannon:
~ Many years ago young Irish girls were blindfolded and sent to the garden at Halloween to pick a cabbage. A ring was then hidden in the colcannon which was made with the picked cabbage. Whoever found the ring on their plate was next to marry.
~ Another old tradition involved unmarried women putting the first and last bite of colcannon into a stocking and hanging it on their front door. The next unmarried man to grace that door was said to be her intended husband.
~ Other traditions include hiding a button, a thimble, a coin and a ring in the colcannon. If you found a button it meant you would remain a bachelor and a thimble meant you would remain a spinster for the coming year. A coin meant you would come into wealth and a ring meant you would get married.
http://www.foodireland.com/recipes/colcannon-cal-ceannann/