family name (late 12c.), later masc. personal name, from Gaelic Dubh ghlais "the dark water," name of a place in Lanarkshire. As a given name, in the top 40 for boys born in U.S. from 1942 to 1971. The name of the city that is the capital of the Isle of Man is the same Celtic compound.

The large, coniferous Douglas fir tree was named for David Douglas (1798-1834), Scottish botanist who first recorded it in Pacific Northwest, 1825. Douglas scheme, Douglas plan, Douglassite, etc. refer to "social credit" economic model put forth by British engineer Maj. Clifford Hugh Douglas (1879-1952).