If you trace the origin of this festival, it goes all the way back to the Edo period.
The origin of this tradition dates back to the Edo period.
事故の起こりは小さなミスだった。
The cause of the accident was a small mistake.
A small misunderstanding became the origin of a big conflict.
発端 stresses the specific incident that triggers a chain of events, while 起こり can refer more generally to the root or start of something.
由来 focuses on the background history behind a name or custom, while 起こり points more simply to the moment or cause something began.
Standard spelling; the most common written form.
Less common variant; acceptable but 起こり is preferred.
Irregular okurigana usage; rarely used in modern writing.
Noun form of the verb 起こる (to occur, to happen), from the stem 起こり. The kanji 起 means 'to rise' or 'to start'.