The Old Gaelic term "dubh", means dark or black, plus "glas" refers to a rivulet or stream. This surname, goes to the Scottish lands of Douglas, south of Glasgow, in Lanarkshire, situated on the Douglas Water.

Most Douglas families were farmers.

In Scotland, the counties of Lanarkshire and Midlothian have the highest number of Douglas families, with the second highest along the southern border of Scotland. In England, the highest percentage of Douglas families are at the northern border with Scotland.

In the United States, the states of New York, Pennsylvania, California, Missouri, Texas, Michigan, Illinois, Tennessee and Ohio have the highest number of Douglas families.

Famous: Kirk Douglas (actor), Aaron Douglas (artist), Gavin Douglas (Scottish poet and bishop), Donald Willis Douglas Sr. (Scottish businessman, founder of Douglas Aircraft Co.),
Keith Douglas (English poet of World War Two), Mike Douglas (entertainer and former TV talk-show host), Jerry Douglas (country music and bluegrass musician), Don Douglas (Scottish film actor), Angus Falconer Douglas-Hamilton (Scottish soldier and posthumous recipient of the Victoria Cross), James Douglas (Scottish-Canadian governor of the colony of Vancouver Island), Stephen A. Douglas (U. S. politician), Shane Douglas (professional wrestler), Norman Douglas (British writer) and Michael Douglas (actor and producer).