Camp (n.) 1520s, "temporary army camp," from French camp, in this meaning from Italian campo, from Latin campus, "open field, level space," specifically "open space for military drill" (see campus). Meaning "a large number" is 1630s. Baseball term, used by John McGraw of New York Giants, first recorded 1887; originally called "the American game." The word comes from the Italian word campo, which means "field" or "level area". This is where their tents would have been set up when they were not on war ships. Before you say it, yes, I know that baseball was not invented in America. But since McGraw introduced the sport to America, it has become one of their most popular pastimes so it makes sense that he would use a term that people would understand. He wanted to give his players something that was familiar to them and could be used as an example for what skills are needed to be successful in his game. He decided to call these skills "cards", which we still use today. Another famous manager who used the term "camp" is William Wrigley, who managed the Chicago Cubs from 1916 to 1930. He started a tradition at Wrigley Field by wearing a captain's hat while playing ball.