It’s one of a kid’s favorite parts of Halloween. There’s no feeling quite like waiting for a stranger to open his or her door so you can scream the words “Trick or treat!” But why do we say it? What does it actually mean? The practice of donning a costume and asking for treats from your Neighbours dates back to the Middle Ages, but back then it wasn’t a game.

During the medieval practice of souling, children and poor people would sing and say prayers for the dead in return for cakes.

Modern trick or treating is a custom borrowed from guising, which children still do in some parts of Scotland. Guising involves dressing in costume and singing a rhyme, doing a card trick, or telling a story in exchange for a sweet. The Scottish and Irish brought the custom to America in the 19th century.

Some have traced the earliest reference of the term trick or treat in print was in 1927, in Alberta, Canada. It appears as if the practice didn’t really take hold in the U.S. until the mid-1930s, where it was not always well received. The demanding of a treat angered or puzzled some adults. Supposedly, in a Halloween parade in 1948 in New York, the Madison Square Boys Club carried a banner sporting the message “American Boys Don’t Beg.” By 1952, the practice was widely accepted enough to be mentioned in the family television show Ozzie and Harriet.

Source: blog.dictionary.com