day of the Boar in the month of the Boar
Refers to the day of the Boar (亥の日) in the tenth month of the old lunar calendar (亥の月). Associated with the 亥の子の祝い festival, where children visit houses and pound the ground with stones or bundles of straw to pray for good health and a bountiful harvest. The term is culturally specific and rarely used outside this context.
See also: 亥の子の祝い
The day of the Boar in the tenth month of the lunar calendar is called Inoko, and the Inoko festival is held in various regions.
day-of-the-Boar mochi
From 亥 (い, boar) + の (possessive particle) + 子 (こ, child). The term is based on the Chinese zodiac sign of the Boar and the lunar calendar. The exact origin of the festival is uncertain, but it is thought to be related to ancient harvest rituals and prayers for children's health.