from Ancient Ayres & Carols CD: The origins of this carol are from pagan times; it was made a Christian carol in the Middle Ages.   Holly was thought to bring good luck to the home and protect it from lightning, witches and evil spirits.  In song, the holly was male and the ivy female.  The holly was connected to the Nativity, the evergreen leaves represented Jesus' eternal life while the white flowers were symbols of the Virgin's Immaculate Conception and of her milk that nourished the infant Saviour.  Ivy was not as joyfully welcomed into the home as holly; it was usually banished to the outside, a practice reflected in many medieval holly and ivy carols where the holly holds mastery over the hall while the ivy shivers outside in the cold.