Year of the Tree - Kinomatoshi

...The story in the Tale of Yamato is famous, and is the origin of the name of Mount Obasute in Sarashina, Shinshu (Mount Kamuriki). In the Tohoku region, the age of 60 is called the "tree-crotch year," and it is said that when people reach this age, they are thrown away by being sandwiched between the legs of a tree on the mountain. The old tale of Mount Obasute is said to have originated in India, and was recorded long ago in the Buddhist scripture, the Zathouzo-kyo. ...

*Some of the terminology explanations that refer to "Ki no crotch year" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…《大和物語》の話は有名で，信濃更級（さらしな）の姨捨（おばすて）山の地名由来になっている(冠着（かむりき）山)。東北地方では60歳を〈木の股年〉と呼び，この歳になると，山の木の股にはさんで捨てると伝えている。姥捨山の昔話はインドが源流とされ，仏典《雑宝蔵経》に古く載せられている。…

※「木の股年」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報