Conker refers to the seed of a British chestnut, and is also the name of a game where you carefully drill a hole through the seed, feed a string through it, tie it so it becomes a tiny, organic wrecking ball. Your goal is to swing your conker at another child's conker until one of them breaks.

It's one of those old timey children's games like chasing a hoop with a stick or playing marbles or smoking cigarettes at the age of 9.