This passage discusses why the term "trick or treat" exists. It mentions how long it has been said, why it is said, and who says it. It also mentions the outcome that is supposed to happen if you say trick or treat and do not receive a treat.
This trick or treating article talks about how halloween was a few different holidays merged together, and how going trick or treating started. It mentions the Christian religion stealing idea's, as well as why it is thought to dress up as someone/something scary.
In this article, it discusses the meaning of trick or treating. It talks about how long it has been a thing, the origin behind it, and a lot of other things surrounding the trick or treating ritual.
A common known thing for the ritual of trick or treating, is that you aren't supposed to be trick or treating past a certain age. In this video, they ask him "are you going trick or treating this year", although he clearly is too old to be trick or treating. This makes him mad, as he knows it's obvious he shouldn't be trick or treating. With his anger, they try to scare him, so he gets his anger out on their prank.