The kadomatsu stems originally from the popular custom of the 'Pine on the Day of the Rat,' in which nobles in the Heian period took pines home during the fondly-held event called the Komatsu-hiki (pulling out small pine trees on the first day of the Rat), and used them to pray for longevity.
もと、平安の貴族達が好んだ小松引きと言う行事で持ち帰った「子の日の松」を長寿祈願のため愛好する習慣から変遷したものである。