The name Doug is a diminutive form of the Scottish name Douglas, which originated from the Celtic words "dubh" meaning "dark" and "glas" meaning "stream" or "water." It was initially a surname derived from a location in Lanarkshire, Scotland, where the River Douglas flows through the village of Douglas.

The earliest recorded use of the name Douglas dates back to the 12th century, with the first known bearer being a nobleman named William de Douglasdale. The Douglas family played a significant role in Scottish history, with several members holding prominent positions and titles, such as the Earl of Douglas and the Duke of Touraine.

One of the most notable figures in Scottish history with the name Douglas was Sir James Douglas, also known as the "Black Douglas" or the "Good Sir James" (c. 1286-1330). He was a close friend and ally of Robert the Bruce and played a crucial role in the Scottish Wars of Independence against England.

Another historically significant figure with the name was Stephen A. Douglas (1813-1861), an American politician who served as a U.S. Senator from Illinois and was a prominent figure in the years leading up to the American Civil War. He was the Democratic Party's nominee for President of the United States in 1860, but lost to Abraham Lincoln.

In literature, the name Douglas appears in Sir Walter Scott's novel "Castle Dangerous," where it is used for the character of Sir John de Walton, also known as the "Douglas Knight." The novel is set in the late 14th century and explores the tensions between Scotland and England during that period.

Other notable individuals with the name Doug include Douglas Fairbanks Sr. (1883-1939), an American actor, screenwriter, and filmmaker who was one of the founding members of the Academy of Motion Picture Arts and Sciences, and Douglas MacArthur (1880-1964), an American five-star general who played a prominent role in the Pacific Theater during World War II and later served as the Supreme Commander of the Allied Powers in Japan during the post-war occupation.

While the name Doug is primarily associated with its Scottish origins, it has gained widespread popularity across various cultures and regions, becoming a common diminutive form of the name Douglas.