Christmas and mistletoe?

Dear fellow authors, do any of you have an idea, where the kissing under the mistletoe comes from?

Fun fact: It is an unknowing bow to the Celtic Druids and preistesses, whose concoction made from the berries of the misletoe saved the ladies from unwanted pregnancies as a result of the Beltane rites. The concotion taken for seven days and then stopped induces an immediate cleansing of the uterus, also known as menstrual bleeding.