ullambana

...It is also called Ullambana Offerings or Ullambana Festival, or simply Ullambana, and is commonly called Tamamatsuri (Festival of the Souls), Shōriyōe (Festival of the Spirits), Obon, etc. Ullambana is said to be a transliteration of the Sanskrit word avalambana, meaning "hanging upside down." According to the Ullambana Sutra, it has been said that the origin of the festival was when Maudgalyāya, in order to save his mother, who had fallen into the realm of hungry ghosts, from the suffering of hanging, set up a ritual to offer to the Three Treasures according to the teachings of Shakyamuni Buddha. However, in recent times this has been denied, with one theory stating that the original word for Ullambana was the Iranian word urvan, meaning the souls of the dead, and that this ritual, which was both a ritual for the souls and a harvest festival, was brought to China when the Iranian Sogdians invaded the country, and was combined with Obon as a harvest festival in the field farming regions, and that the prototype of the Ullambana festival as celebrated today was established when Buddhists linked the day of the dead to Obon.

*Some of the terminology explanations that mention "ullambana" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…盂蘭盆供会，盂蘭盆祭ともいい，略して盂蘭盆と称し，広く魂祭（たままつり），精霊会（しようりようえ），お盆などといわれる。　盂蘭盆はサンスクリットavalambanaの転訛したullambanaの音写とされ，倒懸(さかさづり)の意で，《盂蘭盆経》によると，目連が餓鬼道に落ちた母の倒懸の苦しみを救おうとして，釈迦の教えに従って祭儀を設けて三宝に供養したことが起源であると説かれてきた。しかし最近ではこれを否定して，盂蘭盆の原語はイラン語系の死者の霊魂を意味するurvanであり，霊魂の祭祀と同時に収穫祭でもあったウルバンという祭祀が，イラン系ソグド人の中国進出とともに中国に伝えられ，畑作農業地帯の収穫祭として中元と結合したもので，仏教徒が自恣（じし）の日を中元に結びつけたことによって，今日に伝わる盂蘭盆会の原型が成立したとする説が出ている。…

※「ullambana」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