When the Irish introduced Halloween to America, children celebrated with a night of mild vandalism.
Their bag of “tricks” included breaking or soaping windows or overturning outdoor toilets.
Soon they realized that adults would offer candy or other “treats” to stop these tricks.
They then offered the homeowner a choice of giving them goodies or suffering the consequences.
This mild blackmail demand came as, “Trick or treat?”
The practice of dressing up in costumes and begging door to door for treats on holidays dates back to the Middle Ages in Ireland and Britain and includes Christmas wassailing.
Trick-or-treating is similar to the late medieval practice of souling.
The poor would go door to door on Hallowmas on the 1st of November, receiving food in return for prayers for the dead on All Souls Day on the 2nd of November.