Basically, there are several main meanings of 尔:
1. pronoun. You 你.
2. pronoun. This, that 这,那;这样,那样.
3. adj. / adv. Disdain 不屑.
And 尔尔 usually uses the second and the third meaning.
When using the second, it means: something like ... . 大神尔尔 means something like/related to 大神.
When using the third, it means: disdain. An example is: 不过尔尔