When we think of rookies, we think of first-year players on sports teams and newcomers at the office. It is believed that the term was first used in the American Civil War by the American military. The word began as “reckies”, which was a slang version of the word “recruits”. This was due to a large number of new soldiers who, although inexperienced and barely old enough to drive, were thrust into the war for America. From there, the slang evolved from “reckies” to “rookies” over time.