Is it "soccer" or "football?" Most Americans' usage falls overwhelmingly on the former term, while the rest of the world, including almost all of Asia, South America and Africa, use variations of the term "football."
The term "soccer" is a holdover from the British term "association football." In a 2010 Slate article, writer Brian Phillips explains:
"It's an abbreviation of 'association football.' Both soccer and American football come from the same set of precursor sports, which became popular in upper-class English schools in the early 19th century and spread across the Atlantic. All these games involved advancing a ball through an opponent's territory and scoring at the far end, but the rules varied from place to place. Ultimately, the version adopted as standard in the United Kingdom came to be known as association football, while another set of rules won out in the United States. Thus, the Americans took to calling their gridiron variety football and referred to the British sport by the slang term 'soccer,' derived from the 'soc' in association."
Above is a map showing where "football" and its variants are used, and the (mostly British Commonwealth) countries that use "soccer."