Halloween also had its origin in old belief about

Halloween also had its origin in old belief about the return of the spirit of dead people 结构分析 谢谢回答

主干Halloween had its origin（主卫宾）also副词表示也，同时还。
in old belief about the return of the spirit of dead people是origin的定语，修饰说明是怎样的传统渊源，同理about the return of the spirit of dead people修饰old belief。
整个一个大定语从句，建议从后往前翻译。在古老的信仰中亡者的灵魂回归也是万圣节的一大来源。

搜一下：Halloween also had its origin in old belief about