Why is it a custom to kiss under the mistletoe?

The custom of kissing under the mistletoe may be related to a Scandinavian goddess.  Frigga, the goddess of love in Norse mythology, is strongly associated with mistletoe, which has been used as a decoration in homes for thousands of years.  Mistletoe is associated with many pagan rituals. In fact, the Christian church disliked the plant so much, thanks to its pagan associations, that it forbade its use in any form. Some English churches continued this ban as late as the 20th century!  According to Charles Panati's excellent book, Extraordinary Origins of Ordinary Things, holly became a Christian substitute for mistletoe, which is why we "deck the halls" with it. The sharply pointed leaves in holly were supposed to symbolize the thorns in Christ's crown and the red berries were to symbolize his blood.