Kayuzue (rice porridge stick) (粥杖)
Kayuzue is a stick made by shaving a piece of firewood that was not completely burnt when making kayu (rice porridge) on January 15.
Summary
It is also called 'kayu no ki' (rice porridge wood), but it's also known as iwaigi (celebration wood), bainoki, iwaibo (celebration stick), sachi no ki (wood of happiness) and kezurikake.
Usually, it's made from a willow tree, but it can also be made with pine, cedar, Japanese sumac or walnut.
It is said that if one hits the lower back of a childless woman, she'll give birth to a boy.
In some regions this is called 'dai no ko iwai.'
It also appears in "The Tale of Genji," "The Tale of Sagoromo" and "The Pillow Book."
In the past, women have used the sticks to hit each other.
According to "Kuji Kongen" (Rules of Court, a book on court rules of ceremonies and etiquettes written in the Muromachi period), it began during the Kanpyo era (889 - 898).
It became popular as a game during the Edo period.
In the Tohoku region, there is a custom of carving some pine into a phallic shape 42 to 45 cm in diameter and 90 cm in length, and hitting the buttocks of the newly wedded wife. The kayuzue was also erected at the water inlet of the rice plant nursery as an offering to the deity of the rice field in prayer for a good harvest.
In Shinano Province, the base of a kayu no ki is split vertically into four at Koshogtsu (around January 15); a piece of rice cake, which goes into the rice porridge, is inserted between the split ends and is used to stir the rice porridge.
There is a custom of narizumoku ijime (teasing of narizumoku), in which a cut is made on the bark of narizumoku and rice porridge is smeared over the cut with a kayuzue.