Football sports all involve, to varying degrees, kicking a ball with the foot to score a goal. The most popular of these sports worldwide is association football, more commonly known as just "football" or "soccer". Unqualified, the word football applies to whichever form of football is the most popular in the regional context in which the word appears, including American football, association football, Australian rules football, Canadian football, Gaelic football, rugby league, rugby union and other related games. These variations of football are known as football "codes". The conflicting theories are discussed at length in the main article Football (word).
There are confilicting explanations of the origin of the word "football". It is widely assumed that the word "football" (or "foot ball") references the action of the foot kicking a ball. There is a alternative explanation, which is that football originally referred to a variety of games in medieval Europe, which were played on foot. There is no conclusive evidence for either explanation.
The Ancient Greeks and Romans are known to have played many ball games, some of which involved the use of the feet. The Roman game harpastum is believed to have been adapted from a Greek team game known as episkyros or phaininda, which is mentioned by a Greek playwright, Antiphanes (388–311 BC) and later referred to by the Christian theologian Clement of Alexandria (c.150-c.215 AD). These games appear to have resembled rugby football. The Roman politician Cicero (106–43 BC) describes the case of a man who was killed whilst having a shave when a ball was kicked into a barber's shop. Roman ball games already knew the air-filled ball, the follis. Various forms of 'football' can be identified in history, often as popular peasant games. Contemporary codes of football can be traced back tothe codification of these games at English public schools in the eighteenth and nineteenth century. The influence and power of the British Empire allowed these rules of football to spread, including to areas of British influence outside of the directly controlled Empire, though by the end of the nineteenth century, distinct regional codes were already developing: Gealic Football, for example, deliberately incorporated the rules of local traditional football games in order to maintain their heritage. In 1888, The Football League was founded in England, becoming the first of many professional football competitions. In the twentieth century, the various codes of football have become amongst the most popular team sports in the world.
Games played in Mesoamerica with rubber balls by indigenous peoples are also well-documented as existing since before this time, but these had more similarities to basketball or volleyball, and since their influence on modern football games is minimal, most do not class them as football. Northeastern American Indians, especially the Iroquois Confederation, played a game which made use of net racquets to throw and catch a small ball; however, although a ball-goal foot game, lacrosse (as its modern descendant is called) is likewise not usually classed as a form of "football." The Māori in New Zealand played a game called Ki-o-rahi consisting of teams of seven players play on a circular field divided into zones, and score points by touching the 'pou' (boundary markers) and hitting a central 'tupu' or target.
These games and others may well go far back into antiquity. However, the main sources of modern football codes appear to lie in western Europe, especially England. There are a number of references to traditional, ancient, or prehistoric ball games, played by indigenous peoples in many different parts of the world. For example, in 1586, men from a ship commanded by an English explorer named John Davis, went ashore to play a form of football with Inuit (Eskimo) people in Greenland. There are later accounts of an Inuit game played on ice, called Aqsaqtuk. Each match began with two teams facing each other in parallel lines, before attempting to kick the ball through each other team's line and then at a goal. In 1610, William Strachey, a colonist at Jamestown, Virginia recorded a game played by Native Americans, called Pahsaheman. On the Australian continent several tribes of indigenous people played kicking and catching games with stuffed balls which have been generalised by historians as Marn Grook (Djab Wurrung for "game ball"). The earliest historical account is an anecdote from the 1878 book by Robert Brough-Smyth, The Aborigines of Victoria, in which a man called Richard Thomas is quoted as saying, in about 1841 in Victoria, Australia, that he had witnessed Aboriginal people playing the game: "Mr Thomas describes how the foremost player will drop kick a ball made from the skin of a possum and how other players leap into the air in order to catch it." Some historians have theorised that Marn Grook was one of the origins of Australian rules football.
The word "football", when used in reference to a specific game can mean any one of those described above. Because of this, much friendly controversy has occurred over the term football, primarily because it is used in different ways in different parts of the English-speaking world. Most often, the word "football" is used to refer to the code of football that is considered dominant within a particular region. So, effectively, what the word "football" means usually depends on where one says it. Association football is known generally as soccer where other codes of football are dominant, including: the United States, Canada, Ireland, Australia, and New Zealand. American football is always football in the United States. In francophone Quebec, where Canadian football is more popular, the Canadian code is known as football and association football is known as le soccer. Of the 45 national FIFA affiliates in which English is an official or primary language, most currently use Football in their organizations' official names. The FIFA affiliates in Canada and theUnited States use Soccer in their names.