A nutmeg (or tunnel or panna) is a technique used in football (soccer), in which a player plays the ball through an opponent's legs and retrieves it himself.
The origins of the word are a point of debate. According to Alex Leith's book Over the Moon, Brian - The Language of Football, "nuts refers to the testicles of the player through whose legs the ball has been passed and nutmeg is just a development from this". The use of the word nutmeg to mean leg in Cockney rhyming slang has also been put forward as an explanation. The most likely source, however, was postulated by Peter Seddon in his book "Football Talk - The Language And Folklore Of The World's Greatest Game". He states that 'to nutmeg' was a Victorian verb meaning 'to trick' or 'to fool' and arose after the nutmeg trade gained a reputation for duplicitous goings-on, with vendors selling fake nutmeg. It soon caught on in football, implying that the player whose legs the ball had been played through had been tricked, or, nutmegged.
In northern England the term nutmeg is often shortened to "Nuts" in informal use.
To be nutmegged is commonly seen as showing you are lacking in footballing skill and so amongst amateur players (particularly children) nutmegs are frequently tried so as to show up the opposition player and prove your own skill.