trick or treat

Give me a treat of some kind or I will play a trick on you! (The formulaic expression said by children after they ring someone's doorbell and the door is answered on Halloween. It is now understood to mean simply that the child is requesting a treat of some kind—candy, fruit, popcorn, etc.) "Trick or treat!" cried Jimmy when the door opened. Mr. Franklin opened the door to find four very small children dressed like flowers standing silently on his doorstep. After a moment, he said, "Isn't anyone going to say 'Trick or treat'?"

A greeting by children asking for treats on Halloween and threatening to play a trick on those who refuse to give them. For example, The children went from house to house, shouting "Trick or treat!" [c. 1940]