Book excerpt: Every four years, when the World Cup rolls around, the internet yells at the US that "it's football, not soccer." This short and light-hearted book lays out the contours of the debate, delves into the history of the word "football" and the emergence of the word "soccer," explores some 20th century data on the distribution of the two words and the surprisingly recent origin of the great schism, tells you about all the words the world actually uses to describe the game, gives you a glimpse of the convoluted fate of the word soccer in Australia, and tries to make sense of it all. Stefan Szymanski, co-author of "Soccernomics," is a sports economist who teaches sport management at the University of Michigan. Silke-Maria Weineck, author of "The Tragedy of Fatherhood," teaches German Studies and Comparative Literature at the University of Michigan.