"wet the baby's head"的定义和意义

What is the origin of the idiom "trick or treat" and when to use it?

The idiom "trick or treat" is most commonly associated with Halloween traditions. Its origin can be traced back to the custom of children dressing in costumes and going door-to-door to request candies and treats. The phrase "trick or treat" is used to imply that if a treat or candy is not given, the children may play a harmless prank or "trick" as a form of playful extortion.