When was mistletoe first used in a holiday song?

Mistletoe was first used in songs to honor the legend of the mistletoe plant. The legend is, there was a god named Baldur, son of Frigga. Frigate told every animal and plant not to harm Baldur, but mistletoe escaped hearing this. Then Loki, enemy of Baldur, tricked the blind god of winter into shooting Baldur with an arrow that had a shaft made of mistletoe.