You should remember the following Norse fable the next time you sneak a peck under the mistletoe: Frigga, goddess of love and beauty, wanted to make the world safe for her son, Balder.
Everything on earth promised to do him no harm except the one plant Frigga overlooked, mistletoe. Loki, an evil spirit, made an arrow from the mistletoe's wood and killed Balder. Frigga's tears became the plant's white berries and revived her son.
In her gratitude, Frigga promised to kiss anyone who passed under the mistletoe, just as we do today.