The tradition of bobbing for apples dates back to the Roman invasion of Britain, when the conquering army merged their own celebrations with traditional Celtic festivals.
Apple bobbing, also known as bobbing for apples, is a game often played on Halloween.
The game is played by filling a tub or a large basin with water and putting apples in the water. Because apples are less dense than water, they will float at the surface
Players (usually children) then try to catch an Apple with their teeth. Use of arms is not allowed, and often are tied behind the back to prevent cheating.Tie a piece of string onto the stem of an apple. Tie the string to a high place so that the apple is at the same height as your forehead. Give the apple room to swing back and forth. Standing several feet away and pull the apple towards you until it touches your forehead. Let go and it will swing away from you. Stand completely still and watch the apple as it then swings back towards to you. The apple will not hit you in the face, although it looks like it will. Some of the kinetic energy that causes the apple to move is now converted to potential energy due to gravity. This causes the apple to slow down as it continues to swing.
In Scotland, this may be called "dooking" (i.e., ducking). In northern England, the game is often called apple ducking or duck-apple.
In Ireland, mainly County Kerry, it is known as "Snap Apple", and in Newfoundland and Labrador, "Snap Apple Night" is a synonym for Halloween.
Here is and idea for duck-apple night