A diplomat is a person who helps people who have differing points of view find common ground. In government, a diplomat is an official who represents his or her country in other nations.
The noun diplomat is related to the word diploma, from the Greek diploun, meaning “to fold double.” A diploma is an official paper — something diplomats carry on behalf of their governments. They know about all sides of an issue, which is helpful in times of conflict. You are a diplomat, if caught between Yankees and Red Sox fans, you get them to talk about hockey instead.